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Hellriegel, which had now been generally accepted, viz., that the bacteria possessed the power of absorbing free nitrogen to feed the plants; and explained certain experiments which he saw conducted at Rothamsted to test this view, which experiments made him entertain the idea that it was correct. The next point touched upon was an experiment which he was conducting with an improved Lathyrus (L. sylvestris, Wagn.). Great results were claimed by Dr. Wagner, the improver of the plant, from Lathyrus sylvestris (Linn.); but the experiment, along with others in Britain, had been practically a failure. The grounds of the improvement rested on the great power of the plant to absorb nitrogen as mentioned. The failure of the plant in this climate led him to inquire into the matter and to compare investigations which he had made on native leguminous plants regarding the Bacteria. It appears that the plants produce, or Bacteria is produced, in best form where the plants are growing under favourable conditions for their development, thus assisting prolific development and not extension of geo. graphical area, as is the case with bulbs and creepers on grasses, etc. This was partly confirmed from observations taken from the broom and needlegreenweed, and on a very prolific dwarf pea, which produced a great development of Bacteria, as well as coinciding with results gained at Rothamsted, where a cultivated plant did not produce Bacteria on arid soil, but when 'garden humus was added Bacteria was produced.

To LINCOLNSHIRE BOTANISTS.-- We have pleasure in inserting the following letter :-"I am busy collecting materials for a 'Flora of Lincolnshire.' Would you put a notice in your widely-read paper to say I shall be most happy to receive voucher speci. mens, with localities, dates, &c., for any of our less common or rare plants. Unless I am dealing with past-masters, mere lists are of little use, though thankfully received.”—E. Adrian Woodruffe-Peacock, Cadney Vicarage, Brigg.

any harm, at least not much, but I could not help. thinking that if he had lain helpless through a long frosty winter's night with a gunshot wound, and a broken limb, he would look upon his pleasant day's. sport, as he calls it, in a different light. I suppose there will always be a certain number of persons who find their pleasure in killing for killing's sake, but they should not be encouraged to make a boast of it.w Ward, Southampton.

CLEANING VARNISH.-Can you, or any of your readers, tell me of a good method of cleaning the balsam, asphalte varnish, etc., off spoiled microscope slides, in order to use the glass slips again? I find it a very slow process scraping them clean one by one.A. Verinder.

OPTICAL EFFECT, SCIENCE GOSSIP FOR AUGUST, p. 188.—The optical effect described by H. J; T. is well known as “Purkinje's figures ” (see Huxley's. Elementary Lessons in Physiology). It is not quite easy to understand without some knowledge of the anatomy of the eye, but, briefly, is due to this : the optic nerve, which enters the eyeball at the back (like the stalk of an apple), spreads out over the back of the eye into a delicate nervous layer, the retina. Minute blood-vessels enter the eye at the same spot, and ramify over the inner surface of the retina. When a beam of light is thrown very obliquely into the eye (as H. J. T. describes), these branching bloodvessels are seen, by means of the retina behind them.-M. E. Pope.

SNAKES AND PARASITES.—There are several species of ticks parasitic on snakes, but it would be impossible to identify them from Mr. Tilly's note. Judging from his description, the insects found on the sloughs, may, I think, be mites so often found to be troublesome to cage-birds when due attention is not given to the cleanliness of the cages.-7. Macnaught Campbell.

FLORAL GUIDE TO KENT.-Will some one tell M. B. W. by whom Cowell's “Floral Guide to E. Kent is published, and also the price of the same ? It was mentioned by “Ede” under the heading “Flora of Kent” in the May number of SCIENCE Gossip.-M. B. Wigan.

THE WHITE-FLOWER QUESTION.-A London reader of SCIENCE-GOSSIP-sends me a very interesting letter on this subject. He speaks of baving sound in North Wales, last autumn, Gentiana amarella and the plume thistle both bearing pure white flowers. Symphytium officinale, which I spoke of last month as occasionally bearing white flowers in this neighbourhood, he mentions as growing around Bath much more frequently than the purple variety. In Switzerland and the south of France he has met the lesser periwinkle bearing blue, red, and white flowers, all growing together. The most important part of- this letter relates a curious experience with three plants of Campanula latifolia someone had given him bearing pink bells. He planted all three in his garden, and at the end of the season carefully saved the seed they had produced. From these he had, the following year, plants bearing white, light and dark blue flowers, and only just one or two plants with pink

Since then he has grown all shades and varieties of colour, but never since the first seed sowing any pink. To all these interesting remarks he adds that he has more than once found Anthyllis vulneraria bearing white flowers. I, too, have found this plant with white flowers, but only very sparingly. Besides those plants mentioned last month


“SEA-FOWLING.”—I was both surprised and sorry to see the letter signed, “Sea-Fowler” last month, and I would sain hope that this gentleman's notion of the way to spend a “happy Saturday" will not commend itself to many of your readers. When he tells with evident glee that one gunner shot twentyseven dozen and five harmless birds at one shot, the feeling in the minds of most persons will hardly be one of admiration, but rather of deep disgust, especially when it is remembered that in addition to the number of birds killed, many more must have got away wounded, to die a lingering and painful death. When I read his description of how he shot one of those noble birds, a wild swan, and wounded another which got away and was caught (evidently still alive) next day, I did not wish this self-complacent gentleman


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as sporting into white I have found :-Vinca minor, reared two broods since laying the abnormal egg. - Stachys betonica, Stachys ambigua, Scilla nutans, and When the egg was found a string or vein of the heart. Luzula campestris.-Fred. H. Davey.

like object was protruding through the thick end, and

the egg was broken open in the presence of several CURIOUS PHENOMENON AMONG ROOKS.—The remarks in last month's SCIENCE GOSSIP on mortality

witnesses, including a medical gentleman. It is now

preserved in spirits of wine, and can be seen at the among rooks during the past winter, recalls a curious

above address, and I should like some of your readers phenomenon which occurred in this neighbourhood

to explain it. - Jesse Mitchell. about six years ago among a colony of the same birds. The rookery in question contained at its most

A COUNTING CHIMPANZEE. — The Zoological flourishing state, from thirty to forty-five nests. During Gardens have sustained a serious bereavement in the the spring of 1886, the birds commenced nesting death of “Sally," the black-faced chimpanzee from operations in season, and by the middle of March the west coast of Gaboon, who for eight years has most of the ill-constructed domiciles had approached entertained many thousands of folk of all ages, and completion. But one morning (I think it was March of both sexes, at the popular gardens in Regent's 26th) a painful surprise awaited the proprietor of the Park. The intelligent “Sally” has been the subject estate. Not a caw or sound from the sable tenants of of comment amongst men of science, of sages and the tall elms and ash broke in on his matutinal philosophers, and possibly theologians. Perhaps the slumbers, and on proceeding outdoors he found his most remarkable of her feats was that of counting. feathered friends had taken their flight. By some Sally," in the presence of a crowded room, when unaccountable means they had suddenly awoke to the called upon, say for bits of straw in her cage, would fact that they possessed wings. As though the place give you the exact number you named, up to ten, was under a ban, the whole race of crows kept clear of and the keeper has found her, when alone, count in it. Until the spring of 1889 were the old haunts thus this way up to twenty. If one of the public asked deserted, and then, as if by a preconcerted plan, one for five, six, or nine straws, or whatever quantity up morning a score of the noisy birds alighted on the to ten, she would pick each deliberately up, without tree-tops with much clattering and ado. They held any mistake, put one by one in her mouth until all what seemed to be a conference of some kind. were got together, and then give them into your Chattering, flitting from branch to branch and tree to hand. If asked for a “button-hole,” she would take tree, and a series of graceful gyrations over the tree- a straw, break off part of the stalk, and put the ear tops continued until noon, when the proprietor had into the button-hole of the keeper's coat. She knew the joy of seeing the foundations of a new colony right from left; would use a spoon, and sip with it being laid. To-day the rookery is in a thriving until the cup was empty. She was four years old condition, not containing so many tenants, it is true, when first brought to this country, and was therefore as the one that existed there prior to 1886, but at the twelve years of age. same time running it very close.-Fred. H. Davey.

POISON IN LABURNUM SEEDS.-At Birmingham LARGE FUNGI.—The following is an account of large seven children were taken to Queen's Hospital suffergrowths of two fungi. A specimen of Lycoperdon ing from the effects of having eaten seeds taken from giganteum which I found at Kew (1889), was in the pods of a laburnum tree. They each showed inches long, and weighed 36 ounces; another of the symptoms of poisoning, and emetics had to be ad. same I found at Hampstead this year was 8 inches in ministered. Two of them were so ill that they had diameter, 22} in circumference and weighing 231 to be detained. The children had been playing in

A very large fungus was that of Phallus the churchyard at St. James's Church, Edgbaston, . impudicus, which was 91 inches high, pileus 2 inches and had picked the pods from a laburnum tree and long, and stipe if inches in diameter. This I found eaten them, not knowing that they were injurious. in a copse at Highgate.—Henry E. Griset.

INDIAN LIZARDS.- When I was a lad I had a · collection of Indian stories, I think the name of the

NOTICES TO CORRESPONDENTS. · author was Addison. In it there was a statement to the effect that the common house-lizard, if it happens To CORRESPONDENTS AND EXCHANGERS.-As we now to run over the skin, emits an acrid liquid which publish SCIENCE-Gossip earlier than formerly, we cannot un

dertake to insert in the following number any communications causes a burning sensation and raises a blister. Now,

which reach us later than the 8th of the previous month. I have been in the North-West Provinces of India for

To ANONYMOUS QuerisTS.-We must adhere to our rule of over eight years and must have caught and handled at

not noticing queries which do not bear the writers' names. ? least 200 house-lizards, and I have never found one

To DEALERS AND OTHERS.-We are always glad to treat which emitted any liquid whatever ; more than that, dealers in natural history objects on the same fair and general - at one time a semi-tame lizard lived on my bedstead, ground as amateurs, in so far as the “exchanges” offered are and repeatedly awakened me by running over my face fair exchanges. But it is evident that, when their offers are after mosquitoes, with no result. I should be glad to

simply DISGUISED ADVERTISEMENTS, for the purpose of evading

the cost of advertising, an advantage is taken of our gratuitous know, therefore, if the statement is entirely mythical, insertion of “exchanges," which cannot be tolerated. or true for any sort of lizard.—7. R. Holt.

We request that all exchanges may be signed with name (or REMARKABLE HEN'S EGG.-In reply to your July

initials) and full address at the end. correspondent who enquires as to curious contents of

SPECIAL Note.-There is a tendency on the part of some

exchangers to send more than one per month. We only allow hens' eggs, I may say that I have just seen something

this in the case of writers of papers. far more curious than a pin inside of one, viz :-a

To our RECENT EXCHANGERS.-We are willing to be helpful fleshy substance very nearly resembling a heart in

to our genuine naturalists, but we cannot further allow dis. shape. The egg containing it was laid by a blue guised Exchanges like those which frequently come to us Andalusian hen belonging to Mr. E. Childs, No. II

to appear unless as advertisements. North Parade, Allerton, Bradford, on the 6th of March - last, and weighed. when whole, 41 ounces. It R. H. JAPP.-Apply to Mr. J. King, Seahorse House,

Portland Road, London; or Mr. A. J. R. Sclater, Teign- contained both white and yolk beside the heart. The

mouth, Devon. when is a last year's pullet, is perfectly healthy and has A GENERALISED INDEX.-It is very pleasant to find how



deeply our numerous readers are int.rested in the subject of another General Index. We are aware the vols. of SCIENCEGossip for the last twenty-five years are the best Cyclopædia of Natural History in the world.

D. H. STUART STEWART.-The specimen you sent us of the abnormal var. of the white willow (Salix alba) was very interesting, and we are much obliged to you for it.

D. H. S. S.-"Spiritualism” and “Mesmerism” hardly come within the scope of SCIENCE-Gossip; but we think the Secretary of the London Spiritualist Society would supply you, if asked, with a list of the best books on those subjects.

F. H. P. COSTE.-Your letter must someway have gone wrong, for we have not received it. Please send us your paper.

W. Wilson.–Thanks for your notes. We will look them up.

EXCHANGES. I HAVE twenty-two birds' eggs (various) for exchange. Wanted, fossils from any formation except carboniferous. Walter C. Shields, 30 Garturk Street, Crosshill, Glasgow.

DUPLICATE clutches of curlew, shieldrake, carrion crow, ring ouzel, b. h. gull, sandpiper, snipe, jackdaw, magpie, tree pipit; eggs of bittern, leal, ptarmigan, &c., side-blown. Wanted, clutches, side-blown and with data, numerous sorts. -F. W. Paple, 62 Waterloo Street, Bolton.

Fossils from Barton clay, Purbeck limestone, Kimmeridge clay, and Portland oolite, offered in exchange for those of other localities, rocks, minerals, &c. Apply-A. E. Salter, 8 Venetia Road, Finsbury Park, London, N.

OFFERED, Alycæus sculptilis, Hydrocæna Blanfordiana, Hybocystis gravida, Pupina artata, Diplommatina angulata, Cyclophorus speciosa, Otopoma clausum, Assiminea Francesia, Bithynia marginata, Paludomus regulata, Paludina heliciformis, P. doliarus, Melania lirata, M. tuberculata, Clausilia insignis, from India. Offers wanted in mitra, marginella, or rare land shells.-Miss Linter, Arragon Close, Twickenham.

WANTED, foreign beetles, set or unset, in exchange for many species of British land and freshwater shells, lepidoptera, or good foreign postage stamps.-Mrs. Smith, Monmouth House, Monmouth Street, Topsham, South Devon.

Planorbis corneus, var. albida, Zonites excavatus, var. vitrina, Unio pectorum, Vertigo pygmæa. Wanted, foreign land or freshwater shells, or rare British. -William Moss, 13 Milton Place, Ashton-under-Lyne.

NUMEROUS Ceylon shells, also fifty it.inch corked glass tubes for exchange. Wanted, foreign shells. Please send lists.-J. E. Cooper, 93 Southwood Lane, Highgate, N. WANTED, various species of British vertigos.

Good exchange in other species and varieties of British land and freshwater shells.-E. W. Swanion, Doddington, Sittingbourne.

OFFERED, a mounted and labelled collection of about thirty British land and freshwater shells, in exchange for British birds' eggs not in collection. Full list given on application.E. W. Swanton, Doddington, Sitting bourne.

OFFERED, Donar scortum, Helicon pectinata. Siphonaria concinna, Trochus impervius, from Port Elizabeth. What offers in British marine, land and freshwater, and foreign shells not in collection ?-Mrs. Heitland, The Priory, Shrewsbury.

QUADRANT tandemn tricycle, No. 15, balls, dress-guards, accessories complete. Will exchange for superior microscope. -Kirk, 20 Lombard Street, West Bromwich.

MICROSCOPE, Beck's star, two eye-pieces, 1, #, and correc. tion objectives, double nose-piece, air-pump for mounting objects, Carpenter's “ Microscope," and several other books, together or separate. Engineering books wanted.–Taylor, 26 Marchinont Street, London, W.C.

Would anyone having duplicate natural history specimens or curiosities to spare, towards the formation of a small school museum, kindly communicate with-J. A. Ellis, : Pomona Place, Fulham, London, S.W.

OFFERED, Wood's “Insects at Home," and Stainton's “Manual of British Butterflies and Moths," 2 vols., both equal to new, published at ios. 6d. each.-H. Baker-Browne, Sherrington House, St. Philip's Road, Norwich.

Zonites excavatus, var. vitrina, An. lacustris, Lim. glabra, Hel. cricetorum, vars. instabilis and leucozona, Bul. acutus, and vars, bizona, strigata. and articulata, What offers in other shells for the above?-R. Cairns, Queen Street, Hurst, Ashton-under-Lyne.

DUPLICATES of the following numbers, 8th edition London Catalogue : 39, 46, 100, 1476, 161, 229, 286, 317, 379, 475, 483, 486, 487, 536, 543, 552, 562, 698, 917, 944, 1239, 1584, 1663, 1688, and others, for which I would exchange, in equal number, plants locally abundant not occurring in Yorkshire, or offers.- J. Beanland, 7. Oastler Road, Shipley, Yorks.

I can send rare British shells in return for good mounts of rocks and diatoms, or natural history specimens.-T. E. Sclater, Bank Street, Teignmouth.

ABOUT 1500 herbarium specimens of plants and grasses, chiefly British and Continental, but many from N. America, Asia, China, Australia, Siberia, &c., to exchange for an eight or tep-drawer insect cabinet. Fuller particulars on application to R. Standen, 40 Palınerston Street, Moss Side, Manchester.

For exchange, rare birds' eggs, single or in clutches. Wanted, guillemots, razorbills, gannet, cormorant, skylark, pied wagtail, warblers, tits, hawks, swist, martin, wren, &c. Jas. Ellison, Steeron, Keighley, Yorks.

Avicula hirundo, isocardia cor, Mangelia striolata, wanted in return for rare British and foreign shells, geological speci:

Mutual exchange.-A. J. R. Sclater, M.C.S., 23 Bank Street, Teignmouth.

WANTED, Planorbis lineatus, Pl. nitidus, Pl. nautileus, Pl. parvus, Pl. spirorbis, Pl. complanatus, Physa hypnorum, Linnæa glutinosa, L. involuta, L. truncatula, Paludina contecta, and other freshwater or land shells not in collection, in exchange for Unio tumidus, Sphærium corneum, Pisidium amnicum, Planorbis carinatus, Limnæa auricularia, Limnæa glabra, Ancylus fluviatilis, A. lacustris, Clausilia rugosa, Cl. rugosa, var. dubia, Cl. laminata, Helix virgata, H. hortensis, H. nemoralis, H. pulchella, H. rufescens, and others.-R. D. Laurie, 94 Woodchurch Lane, Birkenhead.

OFFERED, chiton, scabridus, and other shells. Wanted, British shells not in collection. Foreign correspondence invited.-E. R. Sykes, 13 Doughty Street, London, w.C.

DUPLICATES.-H. nemoralis, hortensis, arbustorum, lapicida, Coch. tridens, Claus. laminata, Vertigo pygmaa, &c. Desiderata, land, freshwater and marine shells, and fossils from various formations.-H. E. Craven, Matlock Bridge.

DUPLICATES of H. aspersa, nemoralis, hortensis, Pisana virgata, ca perata, &c., from County Dublin, offered; other species collected if required. Lists exchanged. Correspondence invited. — J. Roland Redding, 4 Vincent Terrace, Glasneivin, Co. Dublin.

Wanted, fossils froin various localities, particularly British and foreign tertiaries. A large number of good duplicates offered in exchange.-Thomas W. Reader, 171 Hemingford Road, Barnsbury, London, N.

OFFERED, microscope slides-anatomical, botanical, insects, diatoms, &c., also unmounted foraminiferous material: also “Fungi,” by Cook, and a few other books. Wanted, slides of rocks, or rock specimens (igneous and metamorphic only), or books on geology, mineralogy, vulcanology, or seismology.R. Ş. Stephens, 25 Fondwych Road, West Hampstead, London, N.W.

Will exchange a photographic enlarging lantern in thorough, working order, also minerals, fossils, shells, botanical specimens, &c., for foreign stamps or cash.-F. Cartwright, 20 Eldon Street, C.-on-M., Manchester.

“Review of Reviews,” and “Strand Magazine" from commencement (wenty numbers of former, eight of larter), the “Universal edition of Shakspeare, also the following paper bound editions:-Kingsley's “Weseward Ho!" " Hypatia," “Yeast,” Lubbock's “Pleasures of Life” (2 vols.), Scott's “Ivanhoe." What offers in books on Christian evidences, stories by J. M. Barrie, &c.-W. H. T., 76 Clifton Street, Lytham.

Unio margaritifer and other British and foreign shells for exchange. Send lists to Mrs. Carphin, i Lauriston Park, Edinburgh.

DUPLICATES.-H. fusca, lamellata, Pupa ringens, &c.' Desiderata, Limnæa involuta, Succinea virescens and oblonga, Helix revelata and obvoiuta, Vertigo Lilljeborgi and Moulinsiana, Acme lineata, and any albine varieties not in collection. -T. A. Lofthouse, 67 Grange Road, Middlesbrough.

BOOKS, ETC., RECEIVED FOR NOTICE. Vols, of the Smithsonian Institution for 1887-89.--"Stammering i Its Nature and Treatment," by Emil Behnke (London: T. Fisher Unwin). - "Le Diatomiste," No. 6 (September) (London: Baillière, Cox & Co.).—“An Account of British Flies (Diptera),” part i. vol. i.-" The Asclepiad."“Quekett Journal."-" Journal of the Geologists' Association.”—“Proceedings of the Bristol Naturalists' Society."Key to the Genera and Species of British Mosses,” by the Rev. H. G. Jameson, M.A. (London: West, Newman & Co.). -"The International Journal of Microscopy and Natural Science" (September). -- " The Essex Naturalist.”—“American Microscopical Journal."-"American Naturalist."-"Canadian Entomologist."-"The Naturalist.”—“The Botanical Gazette." _“The Gentleman's Magazine.”—“The Midland Naturalist."

.“ Feuille des Jeunes Naturalistes.”—“The Microscope."Journal and Proceedings of the Royal Society of New South Wales,” &c., &c.

COMMUNICATIONS RECEIVED UP TO THE 12TH ULT. FROM: W. R.-J. M.-W. C. S.-J. H. G.-J. J. A.-J. C.W. F. C.-A. F.-R. B.-K. E. S.-A. S.-R. M.-F. S. M. J. H. P. C.-A. B.-G. C.-S. A. C.-T. G.-W. W.E. W. S.-E. A.-T.-W. C.-J. R. H.-W. M.-H. E. G.J. E. C.-H. F.-M. E. P.-W. H. Y.-F. W. P.-A. E. S. L. J. S.-J. E. L.-H. C. M.-C. W.-G. S. V.-H.J. P. N.-E. R. S.-F. H. D.-R. D. L.-J. E.-H. E. C.A. J. R. S.-T. E. S.-D. B.-J. R. R.-T. W. R.-R. S. S. -R. S.-J. B.-P. Q. K.-R. H. Y.-W. H. T.-R. C.E. P.-H. B. B.-J. A. E.-C. P.-W.E. C.-Y.C.--A. G. T. -T. E. A.-W. S.-&c., &c.

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HE general pheno- its division, it is developed into the body of the mena of heredity offspring. These are ascertained facts, and form the

well known. only secure foundation for further investigation. Not only do specific Now come the questions, how is it posssible for a characters reappear

single cell, often not more than šo inch in diameter, with absolute accu- to contain all the complex potentialities of the body racy in every gene- of one of the higher animals or plants? How does ration, but those it come to possess these potentialities ? and lastly, slight“ individual how is the adult organism developed from the cell differences,” which containing them? These are the real problems of characterise the heredity, which we have to attempt to solve. In the various individual present state of science it is impossible to furnish members of any definite answers to these questions in terms of species are also very ultimate physical and chemical forces. Nevertheless frequently trans- we can arrive at some conceptions of the modus mitted to the de. operandi of hereditary transmission from a biological scendants of the point of view. We must premise that the first members in which question is the most difficult of all. We know that they first appeared, the tiny cell, often invisible to the naked eye, actually

for more or fewer does contain these potentialities, but it is only in the generations, and with greater or less intensity. In vaguest manner that we can conceive how they are the human race the curved nose of the Bour. contained in its molecular structure. The second bons, and the projecting chin of the Hapsburgs question embodies the problem of the transmission of are examples which are known to all ; and every- hereditary tendencies from one generation to another ; one can multiply instances to any extent from his this we shall call shortly the “problem of transmisown personal experience. How are we to account sion.” The third question embodies the problem of for these wonderful facts? It is sometimes said the development of the hereditary tendencies conthat they are accounted for by a law of persistence, tained in the germ-cell into the actual features of the that “like produces like."

But this is no real organism. This we may call the “problem of desolution at all, it is merely a restatement of the velopment." These two problems are distinct, and problem. The first step in a real solution is to should not be confused, although they are intimately recognise that in ordinary cases of reproduction, a connected. A complete theory of heredity must single cell is separated from the body of the parent, furnish a solution of both. that it subsequently divides and redivides,* and that We must now consider the chief attempts at soluby the growth and differentiation of the products of tion which have from time to time been made by

various biologists. In chronological order they stand • The process of fertilisation, which in the vast majority of

thus :cases precedes segmentation, is here purposely left out of account to avoid complicating the statement of the problem. 1. Mr. Herbert Spencer's theory of “physioThe statement is only literally true in cases of parthenogenesis.

logical units” (“Principles of Biology," vol. i. 1863). No. 323.—NOVEMBER 1891.


2. Mr. Darwin's “ Provisional hypothesis of Pangenesis” (“Variation of Animals and Plants under Domestication,” vol. ii. 1868).

3. Mr. Francis Galton's " stirp" and "gemmule" theory, (“ Proc. Roy. Soc.,” No. 136, 1872, and “Journ. Anthrop. Inst.," vol. 1876).

4. Professor Häckel's “Perigenesis of a Plastidule" (" Ueber de Wellenzeugung der Lebenstheilchen," 1876).

5. Professor Nägeli's “idioplasm” and “germ” theory ("Mechanisch-physiologische Theorie der Abstammungslehre," 1884).

6. Professor Weismann's theory of the “Continuity of the Germ plasm ” (1885).

This does not profess to be a complete list of theories of heredity, but it contains the most resentative and important contributions to the subject.

Mr. Herbert Spencer's and Professor Häckel's theories (which are practically identical) must however be treated separately from the rest. These two authors aim at arriving at general conceptions about the nature of the qualities possessed by the bearers of hereditary tendencies which enable the latter to build up an organism like the parent. They do not give us any particular and definite information on either the process of transmission or the process of development : and hence their hypotheses do not admit of the analysis indicated above.

Mr. Spencer supposes the existence of certain “physiological units," * of which the protoplasm of a cell is composed. They are the ultimate biological units, just as the molecule is the ultimate physical unit, and the atom the ultimate chemical unit. They possess “polarities ” which cause them to build up an organism of a definite shape, just as the polarities of the molecules of a crystal cause the latter to build up a crystal of a definite shape. They are made up of, and are immensely more complex than, the molecules of the chemical substances of which protoplasm is composed, and "in each organism the physiological units produced by this further compounding of highly compound atoms [molecules] have a more or less distinctive character.t We must conclude that in each case, some slight difference of composition in these units, leading to some slight difference in their mutual play of forces, produces a difference in the form which the aggregate of them assumes.” I The sperm-cells and egg-cells are simply “vehicles in which are contained small groups of the physiological units in a fit state for obeying their proclivity towards the structural arrangement of the species they belong to." § Any modification of the function or structure of any part of an organism will cause, “some cor

responding modification” of “the structures and polarities of its units." These modified polarities will tend to re-establish equilibrium between the forces of the aggregate and those of the unit, and hence separated groups of units will tend to build up an organism modified in a similar manner to the one from which they were derived. Thus does Mr. Spencer attempt to give us a conception of the manner in which he imagines both ordinary inheritance and also the inheritance of acquired modification, can take place. Professor Häckel substitutes"6

‘plastidule" for “physiological unit,” and “vibrations” or “undulatory movements ” for “polarities”; but apart from these changes of terminology, his hypothesis appears to be substantially the same as that of Mr. Spencer, which, however, he seems not to have read.*

Various criticisms can be obviously made. In the first place a living organism is not a crystal, nor do its ultimate living constituents-call them physiological units or protoplasmic molecules or what you will act in an exactly similar way to the molecules of the latter ; and although Mr. Spencer carefully avoids stating that they do, this is what he practically assumes in his explanation of normal heredity and the repair of lost parts. But he also states that a modification of structure or function causes modified structure and polarities of the physiological units, and that in consequence separated groups of the latter build up a similarly modified organism. But if this is sometimes the case, why is there no hereditary effect in the case of the loss of those parts of organisms which are normally repaired ? such as the leg of a newt, or the tail of a lizard or of a tadpole. There is surely a sufficient modification here to "impress some corresponding modification on the structures and polarities” of the physiological units. And on the former assumption, why are lost parts not always repaired ? Why does not a man grow a new leg when he has lost one? Where is the difference between the two sets of cases ? It has never (on Mr. Spencer's theory) been pointed out. As a matter of fact, the two explanations are mutually exclusive. And even supposing they were not, they both depend upon

the unjustifiable assumption of absolute solidarity between the parts of an organism. No doubt the relations of the different parts of the body to each other and to the whole are highly important, but it is impossible to maintain that a slight modification of any given part necessarily affects permanently every other part ; and this is what Mr. Spencer's assumption practically amounts to. And we have never been furnished with a clear and definite account of the mechanism by which the effects of such modifications are propagated through the body to distant cells-cells, too, which are often fully developed and have become perfectly quiescent years before. This

* Professor Michael Foster (“Text-Book of Physiology," ffth edition, Introduction, pp. 5, 6) has adopted this conception in order to explain the facts of metabolism, and the differences of different tissues. He differs from Mr. Spencer in this last part of the hypothesis. + Cf. the “idioplasm” of Nägeli.

Principles of Biclogy,” vol. i. p. 183.
Ibid. p. 254...

* I am not acquainted with Professor Häckel's hypothesis at first hand.

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