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To our RECENT EXCHANGERS.-We are willing to be helpful to our genuine naturalists, but we cannot further allow dis. guised Exchanges like those which frequently come to us to appear unless as advertisements.
H. E. G.-Get Bennett's “Manual of Cryptogamia," pub. lished by Longmans at, we believe, 6s.
C. H. Betts.-We are much obliged by your complimentary query, but we beg to say that, as a magazine or otherwise, ŚCIENCE-Gossip is perfectly free, and sails under no auspices except those of publisher, editor, and generous and loyal contributors. It has been issued thus for twenty-six years, and perhaps no other popular scientific journal has such a worldwide or large circulation. Our views are perfectly independent, although we endeavour to make them comprehensive and sympathetic.
c. T. Musson (Hawkesbury, N.S. Wales). -Many thanks for specimens of green roses.” They are not uncommon, and on this side of the world we have known forists who made money by cultivating green rose trees. Of course, it is a question of return of the petals to the foliar or green condition. The real inquiry ought to be as to whether this greenness is due to the presence of chlorophyll, or otherwise.
EXCHANGES. ROTIFERA.-Can anyone send me specimens of Callidina pigra, C. symbiatica, or C. Liebhardti? Correspondence invited.-David Bryce, 37 Brooke Road, Stoke Newington Common, London, N.
WANTED, a good selection of mounted histological slides; also minerals and geological mounted slides. A reasonable price given.-W. F. Crews, c.0. F. F. and Co., Rangoon, Burmah.
WANTED, all kinds of good unmounted micro material and microscopical books, in exchange for choicest microscopic slides of every variety. Foreign correspondence solicited. R. Suter, 5 Highweek Road, Tottenham, Middlesex, England.
Sphærium lacustre, Helix fusca, Pisana pulchella, Clausilia laminata, Balia perversa, and many others. Wanted, species and varieties of many land and freshwater shells.-H. Downes, University Union, Edinburgh.
L. C., 8th ed.:-109, 115, 193, 272, 315, 396, 493, 574, 579, 611, 648, 691, 966, 976, 982, 1101, 1134, 1154, 1200, 1422, 1439C, 1459, 1529, 1538, 1953, 1759, &c. Lists invited.-W. Biddis: combe, 60 St. James's Place, Plumstead, S.E.
LAND molluscs from the Bernese Oberland, in exchange for foreign helices from any country. Also Helix elegans from the only British locality.-Rev. J. W. Horsley, Woolwich.
WANTED for the museum, typical collections of minerals, sea-weeds, corallines, or lichens; must be correctly named. Will give in return typical collections of beetles, butterflies and moths, or cases.-S. L. Mosley, Beaumont Park Museum, Huddersfield.
OFFERED, L. C., 8th ed. :-36, 47, 101, 105, 1076, 116, 121, 141, 1766, 193, 221, 229, 240, 291, 335, 336, 338, 341, 483, 536, 538, 562, 576, 611, 635, 698, 854, 859, 863, 873, 901, 918a, 9286, 944, 957, 99, 970, 973, 1189, 1194, 1196, 1212, 1224, 1232, 1344, 1421, 1483, 15186, 1563, 1593, 1629, 1530, 1688, 1743, 1753. 1772, 1794, 1813, 1845. List of desiderata on application to–J. A. Wheldon, 9 Chelsea Road, Walton Vale, Liverpool.
OFFERED, Cassell's “Familiar Wild Flowers,” forty parts, and “Fishing Gazette" for 1889-91. Will accept natural history specimens or books in exchange, or other offers. H. Fisher, Stodman Street, Newark, Norts.
WANTED, entomological cabinet, store-boxes, &c. Can offer in exchange about tilty, species of British birds' eggs, mostly in clutches, and a few with nests; also fossils from secondary and tertiary rocks.-W. D. Carr, Lincoln.
What offers for about fisty kinds of animal hairs, fish scales, exotic and British lepidoptera, and dragonflies' wings, &c. Also about forty British birds' eggs (unnamed). Wanted particularly, land and freshwater shells, and the following books: Rye's “Beetles," Rimmer's “Land and Freshwater Shells," Taylor's. “. Aquarium,” &c.; condition immaterial so long as no pages missing.-H. Durrant, 4 Boulton Road, West Bromwich. WANTED, botanical slides, good sections.
A packet of unmounted material from New Zealand, of which I have six different, will be given in exchange for each slide.-W. A. Gain, Tuxford, Newark.
WANTED, a good copy of Beale's "How to Work with the Microscope,” in exchange for a collection of 258 Swiss plants, including some of the rarest : Anemone Halléri, Ranunculus glacialis, Dianthus superbus, Potentilla frigida, Leontopodium alpinum, Artemisia mutellina, Hieracium aurantia. cum, Gentiana glacialis, named and mounted.
Bernard Stracey, 45 Fountain Hill Road, Edinburgh.
For exchange, bred specimens of ruby tiger (A. fuliginosa), six vols. SCIENCE-Gossip, including two with coloured plates, and McAlpine's "Botanical Atlas," unbound. Wanted, books, tricycle, and a few good diatom and botanical mounts.-J. C. Blackshaw, 179 Penn Road, Wolverhampton.
WELL-MOUNTED palates of British land and freshwater shells in exchange for good foreign land or freshwater shells. -William Moss, 13 Milton Place, Ashton-under-Lyne.
DUPLICATES.-T. haliotidea, H. Cantiana, var, albida, H. virgata, vars. alba and albicans. H.Cartusiana, H. caperata, var. major, P. secale, and C. laminata, var. albinos. Desiderata, good local forms of H. nemoralis, H. hortensis, H. arbustorum, H. rirgata, and H. ericetorum, or offers.C. H. Morris, Lewe, Sussex.
OFFERED, a large selection of mosses, juncace, carices, hepaticea, in exchange for lichens (named), or a copy of Hobo kirk's “ British Mosses" would be acceptable.-Albert Downie, 40 Dallfield Walk, Dundee.
WANTED, some one to cut and polish a few geologica} specimens. Will give Alston Moor minerals for doing it.William Hetheringion, Nenthead, Alston Moor, Cumberland.
Good encrinite heads and palatal teeth of Psephodus magnus from Carboniferous limestone, Vertigo pygmæa, and Zonite excavatus, var. vitrina. Wanted, foreign land shells.Cairns, Queen Street, Hurst, Ashton-under-Lyne.
SCIENCE-Gossip for 1869, “Brit. Assoc. Handbook of Man. chester,” and “The Point and Line." Wanted, copy of "L. C.” 8th ed., &c.-G. H. B., Thornlea, Cambridge.
DUPLICATES.-H. nemoralis, hortensis, arbustorum, ericetorum, Cantiana, caperata, Coch. tridens, Claus. laminata, Vertigo pygmaa, &c., fossils from carboniferous limestone and Yoredale shale, Derbyshire minerals. Desiderata, land, freshwater and marine shells, and fossils from various formations.-H. E. Craven, Matlock Bridge.
ASTRONOMICAL telescope, at-inch object-glass, on solid brass table stand with steadying rod, having rack and pinion adjustment, very highly finished. Want good monocular or binocular microscope. State maker's name. - Dr. Taylor, 26 Marchmont Street, London, W.C.
DUPLICATES.-Fine Sphærium ovale and S. rivicola, Unio pictorum, U. tumidus, Paludina vivipara, Limnaa stagnalis, Anodonta cygnea, Helir arbustorum, Planorbis corneus. Pupo marginata, &c. Desiderata, other British land and freshwater shells.-R. Dutton, Piccadilly, York.
Duplicate clutches of goldtinch, sociable plover, Montague harrier, water-rail, ring ousel, goldcrest, crested uit, coil bunting, eider, duck, and eggs of capercaillie, widgeon, scaup, twite, hen harrier, merlin, &c. Desiderata, many kinds commoner eggs. - Jas. Ellison, Steeton, Keighley.
WANTED, varieties of British land and freshwater shells. Can offer very fine Pupa secale, B. obscurus, vars. strigata and bizona, Balia perversa, and many others. A. Alletsee, 1 South Villas, Kensington Road, Redland, Bristol.
DUPLICATES. - Emarginula rosea, Trochus Montacuti, exasperatus, striatus, Rissoa reticulata, calathus, inconspicua, cancellata, lactea, Cæcum glabrum, Helir revelata, Cyclostrema nitens, &c. Wanted, British marine and foreign shells not in collection. — Brockton Tomlin, The Green, Llandaff.
Fossil shells from the Berton clay, Purbeck limestone, and Kimmeridge clay, offered in exchange for fossils, minerals, and rocks of other formations. Address - Mr. A. E. Salter, 8 Venetia Road, Finsbury Park, N.
DUPLICATE clutches of little bittern, curlew, shieldrake, b.-h. gull, swallow, cuckoo, marsh-tit, Manx shearwater, reed warbler, magpie, jackdaw, whitethroat, lesser redpole, tawney owl, chaffinch, eggs of hoopoe, lesser whitethroat, guillemot, razorbill, widgeon, &c. Desiderata, clutches, side-blown and with data.-F. W. Paple, 62 Waterloo Street, Bolton.
H. lamellata, H. fusca, P. ringens, An. lacustris, and numerous other species offered for any shells, British or foreign, not in collection. Also fossils for others, or offers. Foreign correspondence specially desired.- Rev. John Hawell, Ingleby Greenhow Vicarage, Middlesbrough.
BOOKS, ETC., RECEIVED FOR NOTICE. “British Edible Fungi," by Dr. M. C. Cooke (London: Paul, Trench, Trübner & Co.).-"Physical: Geology and Geography of Ireland,” by Professor Ed. Hull (London: Stamford). -" Le Diatomiste," No. 6 (September) (London: Baillière, Cox & Co.).—“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.
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BY A. G. TANSLEY.
[Continued from p. 244.]
R. FRANCIS GAL to explain the problem of development. But as we
TON'S theory of shall presently see, his hypothesis differs in an
that many gemmules must remain altogether latent endeavour to show, during the lifetime. He conceives of the stirp as however, that
dividing, before the beginning of embryonic developneither of these ment, into two parts, first, those gemmules which are representations is predominant, and which enter upon embryonic correct. Mr. Gal.
development, and secondly the “residue,” which ton's theory, in remain latent in the body, and from which the reprodeed, stands in an ductive elements are mainly if not solely derived. important manner Here we are presented with an entirely new solution intermediate be of the problem of transmission. Mr. Galton explains tween “Pangene.
the difficulty by supposing not that the bearers of the
sis” and “the con hereditary tendencies are redeveloped from the cells tinuity of the germ-plasm," but it is a perfectly distinct of the body in each generation, but that there is a theory. In 1872 the main ideas were promulgated, continuity of gemmules from generation to generation, but a fuller account was published in 1876.
and that the structure of each organism is built up Mr. Galton sets out with a conception of the organism by certain representative gemm les, which achieve as composed of microscopic “organic units.” He
Mr. Galton remarks that there are does not distinctly state whether these correspond to two classes of facts of heredity: (1) the transmission cells, but with our present knowledge it seems of inborn or congenital peculiarities, also congenital probable that, in many cases at least, they would in one or more ancestors, (2) the transmission of have to represent portions of cells. This conception those inborn peculiarities not congenital in ancestors, he thinks is necessitated by the facts of the inheritance but acquired owing to changes in the conditions of of microscopic characters, and the inheritance of
life. He points out that Pangenesis was especially these from different parents.
devised to explain the latter class; but he remark supposing that each organic unit is developed from a that the majority of these cases may be looked upon separate germ or “gemmule.” The whole collection as "a collection of coincidences," that it is “indeed of gemmules in the fertilised ovum he calls the stirp. hard to find evidence of the power of the personal Hence we see that he adopts the preformation theory structure to react upon the sexual elements that is not Lloyd Morgan's “Animal Life and Intelligence," p. 135.
open to serious objection," and that “we might almost + Wallace's "Darwinism,” p. 443.
reserve our belief that the structural cells can react No. 324.- DECEMBER 1891.
He explains this by a
on the sexual elements at all.” Hence Mr. Galton Professor Nägeli's theory of heredity (with which only adopts the theory of Pangenesis as supplementary 1 am only acquainted through Professor Weismann's and subordinate, to explain the cases
criticism) is intimately bound up with his ideas of quired characters may possibly be transmitted; he phylogeny or race-development, with which we are explains the primary facts of heredity by his theory not concerned, but of that portion which deals with of the continuity of the reproductive elements. By the two problems which we are keeping before us, a adopting this position he dispenses with Darwin's short account must be given. conception of gemmules representing every stage in Professor Nägeli’s hypothesis reminds us to some ontogeny, and thus although he believes the “or extent of Pangenesis, and to some extent of Mr.
Involves such transmission.
Involves such transmission.
H. Spencer 1863 “ Physiological The assumed solidarity of the or
ganism. A separated group of
physiological units or plastidules, E. Häckel 1876 | Perigenesis of by means of the “polar forces
a Plastidule. or“ vibratory movements com
mon to them and to the other
gemmules from gemmules re-
every cell ever
germs (“ An-
Involves such transmission.
recognise the separate problems of transmission and development.
ganic units” of adult structure to be preformed in the germ, we can conceive of the separate “representative” genımules developing epigenetically into the adult structure. This does away with the difficulty expressed by Professor Weismann in the criticism above quoted.
Mr. Galton's theory approaches Professor Weismann's, but is nevertheless distinct from the latter. We shall discuss the points of difference more fully hereafter, and reserve our criticisms till then.
Spencer's hypothesis, but to its author belongs the credit of originating the valuable conception of “idioplasm.” Prosessor Nägeli supposes that there is a network of solid substance extending throughout the body, which determines the specific character of the organism. This is idioplasm, and although differing qualitatively in different species, its nature is fundamentally the same in the different parts of the body of the same organism. The development of an organism is dependent upon the successive activity of
different parts of the idioplasm ; when any part has become active, the tension between that part and the rest becomes such that further growth of that part cannot take place, but the next part begins to grow actively.
The idioplasm is composed of germ: (* Anlagen ') of the different structures, each of which, reacting under the stimulation of the growth of the previous ones, becomes active in its turn and produces the corresponding structure. This is very like Darwin's conception of the development of gemmules. When all the stages of ontogeny have been passed through, the idioplasm returns to its original state-never having differed from it except in respect of "conditions of tension and movement"-and produces germcells. This is the theory of the “cyclical development of the germ-plasm” and reminds one of Mr. Spencer's views on physiological units, which are also apparently fundamentally the same in different parts of the body. If, however, there is such a substance as idioplasm, it is to be found in the cell nuclei, as we shall see hereafter, and cannot be conceived of as forming a network throughout the body. Furthermore it is impossible to conceive of the difference between the idioplasm of, for instance, a muscle-cell and a white blood-corpuscle as consisting in a mere difference of "conditions of tension and movement." Professor Nägeli adopts the hypotheses of redevelopment and preformation in essence, though he considerably modifies former conceptions.
Professor Weismann's hypothesis of the continuity of the germ-plasm differs from all former theories by his complete adoption of the epigenetic explanation of ontogeny, and of the explanation by continuity of the germ-plasm of the problem of transmission. He supposes that a substance (germ-plasm) with a specific molecular structure is handed on from generation to generation. Part of this, at the commencement of segmentation, is separated off for the building up of the bodily structure, the rest is preserved unchanged and is eventually transmitted to the sexual cells. That portion which is converted into the idioplasm of the body undergoes an actual change of molecular structure at each stage of ontogeny.
We are now in a position to arrange the various theories of heredity we have considered in a table, which shall show at a glance their kind of explanation of the general problems of heredity, and as an outcome of this their bearing upon the question of the transmission of acquired characters. We see at once from the table (p. 266) that (apart from Mr. Spencer's and Professor Häckel's hypotheses) those theories which explain the problem of transmission by supposing that redevelopment of the specific bearer of hereditary tendencies takes place in each generation, involve the transmission of acquired characters, while those which explain the problem of
transmission by supposing that this specific substance
continuous from generation to generation do not. And it is obvious that this must be so. We can form no clear conception of how it is possible for acquired characters to be reproduced as such in the next generation except by the aid of the hypothesis of redevelopment. Mr. Spencer's and Professor Häckel's theories do not furnish such a clear conception. And the clearest expression of the hypothesis of redevelopment is undoubtedly to be found in Mr. Darwin's theory of Pangenesis ; for Prosessor Nägeli's theory does not present us with a sufficiently definite and intelligible mechanism.
The issue, then, seems at present really to be between Pangenesis and a theory of continuity of the specific hereditary tendency-bearing substance. But we have seen that there are objections of the gravest kind to the hypothesis of Pangenesis. It is therefore incumbent upon us to examine more in detail the theory of continuity as it has been expressed by Mr. Galton and Professor Weismann. If any form of it explains the general facts of heredity with ease and certainty, and can be shown to be in accord with the general tendency of research, we shall be justified in accepting it, provisionally at least; and we shall be further justified in considering that this is, so far as it goes, good evidence against the transmission of acquired characters. It is perfectly true that the transmission of acquired characters may take place, and yet that we may be unable, at present, to arrive at a clear conception of the mechanism by which it is brought about ; but it is also true that if, in the absence of direct affirmative evidence on the point, and from quite other considerations, the theory which excludes such transmission can be shown to be more likely to be correct than the theory which involves it, we are forced to consider this fact alone as evidence which negatives its probability.
O Rhizopod belonging to the sub-order Filosa
has a more elegant and complex shell than that of any of the seven species of Euglypha, which is characterised by the colourless, transparent test, being made up of oval plates, overlapping in such a way as to form very definite and beautiful patterns, and by being further ornamented by numerous spines or hairs. Fortunately, some of the species are very common and widely distributed, being found in the ooze of most ponds and ditches, among Sphagnum, and on dripping rocks with mosses and Algæ. During the short period I have devoted to the special study of the Rhizopods, I have found hundreds of individuals belonging to two species, Euglypha alveolata, and E. ciliata. The former is the commoner species here, and is a very variable form, both
as regards size and definiteness of structure. Ordinarily, the shell is transparent and colourless, eggshaped, with the narrow end truncated by the mouth ; but in some of the larger ones the lower end is pro
nged, when it appears somewhat flask-shaped. These larger forms I have not yet been able to find, but in these, according to Professor Leidy, " the shell is clearly seen to be composed of regular plates, of nearly equal size, os oval form, arranged alternately in longitudinal rows and overlapping at their contiguous borders. This arrangement produces the impression of hexagonal areas defined by zones of smaller elliptical areas (see Fig. 215). In the smaller forms, which I have procured in abundance from among mosses and Algæ in several of our
larger forms from Sphagnum are as much as the god of an inch in length.
Fig. 214. Specimen with sarcode retracted, show. ing hourglass-like contraction : test with diamondshaped markings.
Fig. 215. Prettily-marked form, pseudopodia extended.
Fig. 216. Another, with hourglass-like contraction of sarcode ; pseudopodia extended ; with four spines.
Euglypha ciliata is exclusively of sphagnous habitat. It very closely resembles E. alveolata, but the shell is more compressed, and has a fringe of hairs or spines round the top and sides. These spines vary considerably, not only in numbers, but also in length and strength, and in the amount of surface they cover, In most other respects it is identical with E. alveolata.
Fig. 217. Empty colourless test, structure obscure, but indicating overlapping plates.
Fig. 218. Another specimen, with finer and more numerous spines, covering nearly the whole surface.
Trinema enchelys is one of the smallest, and also
Fig. 215.—Ditto, pseudo
Fig. 216.-Specimen of ditto with four spines; pseudopodia extended.
wells, the structure is not, by any means, so clearly defined ; indeed, in the majority of individuals, the structure of the shell is very obscure, and, when seen at all, frequently appears only as fine, diamondshaped markings. Some specimens show from two to six thorn-like spines of about equal length, attached to the shell near the sundus or top; others these appear to have been rubbed off. The sarcode is generally colourless, though sometimes yellowish or brown, occupying most of the shell, though often constricted in the middle, in an hourglass manner, as in Figs. 214, 215 and 216. Nucleus large, situated near the fundus. The size of this species, like that of most Rhizopods, varies considerably ; my specimens averaged about orsós of an inch in length, but the
one of the commonest, of the testaceous Rhizopods. It is a rare thing to find a pond or ditch which will not furnish specimens of this ubiquitous animal. In squeezings from Sphagnum I have procured them in thousands, and, according to the authority previously quoted, “it is often found in the earth about the roots of mosses and other plants, even in such places as roadsides, on the bark of trees, old wooden or thatched roofs, and in the crevices of pavements of cities." The shell is transparent, colourless and pouch-like, with the oral end generally the smallest. The mouth is circular, sub-terminal and inverted. In a front or back view, the shell of ordinary specimens is more or less ovoid, of homogeneous, chitinoid membrane ; but in the larger forms, from sphagnous swamps, the shell is made up of circular plates with beaded borders. The large, handsome varieties I have been unable to procure, the nearest approach being an empty shell, from Sphagnum, with delicate punctations arranged in circles on the shell, Fig. 222. Although not a striking form, yet the glassy shell is beautiful from the elegance of its curyes. A nucleus