The relations exhibited by fully grown animals and plants with transitional or embryonic stages of other animals and plants, had attracted the attention of anatomists at the time of Lamarck. Some naturalists deduced from this now universally observed phenomenon, that the lower types of animals were merely repressed conditions of the higher, or in other words, were embryonic stages become permanent. But the resemblances do not usually extend to the entire organism, and the parallels are so incomplete, that this view of the matter was clearly defective, and did not constitute an explanation. Some embryologists, as Lereboullet and Agassiz, asserted that no argument for a doctrine of descent could be drawn from such facts.

The speaker, not adopting either view, made a full investigation into the later embryonic stages, chiefly of the skeleton of the Batrachia, in 1865, and Prof. Hyatt, of Salem, Mass., at the same time made similar studies in the development of the Ammonites and Nautili. The results as bearing on the doctrine of evolution were published in 1869 (in "The Origin of Genera"). It was there pointed out, that the most nearly related forms of animals do present a relation of repression and advance, or of permanent embryonic and adult type, leaving no doubt that the one is descended from the other. This relation was termed exact parallelism. It was also shown, that, if the embryonic form were the parent, the advanced descendant was produced by an increased rate of growth, which phenomenon was called acceleration; but that, if the embryonic type were the offspring, then its failure to attain to the condition of the parent is due to the supervention of a slower rate of growth; to this phenomenon the term retardation was applied. It was then shown that the inexact parallelism was the result of unequal acceleration or retardation; that is, acceleration affecting one organ or part more than another, thus disturbing the combination of characters which is necessary for the state of exact paral lelism between the perfect stage of one animal and the transitional state of another. Moreover, acceleration implies constant addition to the parts of an animal, while retardation implies continual subtraction from its characters, or atrophy. He has also shown (Method of Creation, 1871), that the additions either appeared as exact repetitions of preexistent parts, or as modified repetitions, the former resulting in simple, the latter in more complex organisms.

Professor Hæckel, of Jena, has added the keystone to the doctrine of evolution in his Gastræa theory. Prior to this generalization, it had been impossible to determine the true relation existing between the four types of embryonic growth, or, to speak otherwise than that they are inherently distinct from each other. But Hæckel has happily determined the existence of identical stages of growth (or segmentation) in all of the types of eggs, the last of which is the gastrula; and beyond which the identity ceases. Not that the four types of gastrula are without difference, but this difference may be accounted for, on plain principles. In 1874, Hæckel, in his "Anthropogenie," recognizes the importance of the

irregularity of time of appearance of the different characters of animals during their period of growth, as affecting their permanent structure. While maintaining the view that the low forms represent the transitional stages of the higher, he proceeds to account for the want of exact correspondence exhibited by them at the present time, by reference to this principle. He believes that the relation of parent and descendant has been concealed and changed by subsequent modifications of the order and appearance of characters in growth. To the original simple descent he applies the term palingenesis; to the modified and later growth, cœnogenesis. The causes of the change from palingenesis to cœnogenesis, he regards as three, viz: acceleration, retardation, and heterotopy.

It is clear that the two types of growth distinguished by Prof. Hæckel are those which had been pointed out by Prof. Cope in "The Origin of Genera," as producing the relations of "exact" and "inexact parallelism;" and that his explanation of the origin of the latter relation by acceleration or retardation is the same as that of the latter essay. The importance which he attaches to the subject was a source of gratification to the speaker, as it was a similar impression that led to the publication of "The Origin of Genera" in 1869.

It remains to observe that the phenomena of exact parallelism or palingenesis, are quite as necessarily accounted for on the principle of acceleration or retardation, as are those of inexact parallelism or cœnogenesis. Were all parts of the organism accelerated or retarded at a like rate, the relation of exact parallelism would never be disturbed; while the inexactitude of the parallelism will depend on the number of variations in the rate of growth of different organs of the individual, with additions introduced from time to time. Hence it may be laid down, that synchronous acceleration or retardation produces exact parallelism, and heterochronous acceleration or retardation produces inexact parallelism.

In conclusion, it may be added that acceleration of the segmentation, the protoplasma or animal portion of the primordial egg, or retardation of segmentation of the deutoplasma or vegetative half of the egg, or both, or the same relation between the growth of the circumference and center of the egg, has given rise to the four types which the segmentation now presents.

An analysis of the laws of evolution may be tabulated as follows:

Exact repetition.

Acceleration, which proceeds by Modified repetition.

Retardation, which proceeds by

Heterotopy.
Exact atrophy.

Inexact atrophy (or senility),*

and each of the methods may be either of Exact parallelism, the product of Palingenseis, which is synchronous; or Inexact parallelism, the product of Coenogenesis, which is heterochronous.

3. Mimicry in Butterflies explained by Natural Selection; by S. H. SCUDder. (Proc. Amer. Assoc., Buffalo.)-Fritz Müller,

So called by Professor Hyatt.

whose contributions to science are always worthy of especial attention, endeavors in a recent German periodical to show how the phenomena of mimicry in butterflies may be explained by the theory of natural selection. He bases his inquiries upon the species of Leptalis found in southern Brazil; and although, as will appear below, he adduces reasons for believing the primitive stock to have been banded, and not, like most of the family to which the genus belongs, simple white butterflies, he commences by showing how even such an extreme change could be wrought out by the survival of the fittest in the struggle for existence. "Should,” he remarks, "the first unimportant variations from the original white color (of the Pierids) be useful only in attracting to their possessors, at a little shorter distance, the attention of enemies flying constantly overhead, they would become more and more useful, and cause their possessors to become continually more abundant in proportion to the type, they could therefore serve as the basis for the gradual formation of a resemblance fit to deceive even the sharp eyes of birds scanning the swarms of Ithonias (the butterflies imitated by some Leptalids) for booty." Further on he asserts that "the acceptance, as the starting point in the origin of mimicry by natural selection, of a resemblance having its beginning at such a distance, can scarcely be shaken by a single known case. It should moreover not escape attention that the sharpsightedness of enemies is itself also a quality at first gradually acquired in the struggle for existence, and one which must increase from the very fact that by protective coloring, mimicry, &c., the persecuted species escapes the less sharp-sighted pursuer. This ever increasing sensitiveness and sharpsightedness of the pursuer on the one hand explains the wonderful completeness of many natural imitations, and, on the other, makes the acceptation of an originally very slight resemblance the less hazardous."

Fritz Müller insists, as all writers on the subject have done, upon the similar geographical distribution of the imitating and the imitated species, as a necessary concomitant of mimicry, but instead of believing, with the other authors, that the Leptalids have become poor flyers in their imitation of the feeble-winged Ithonias; he holds that the wretched powers of flight possessed by the species of Leptalis have been the very cause of mimicry; the insects needed mimicry the more the poorer flyers they were. Mimicking species, of course, stand between their original type and the mimicked species; and, since mimickry is often confined to the female, we should expect in such cases to find the following series: original form, male of mimetic species, female of same. Species mimicked. In his vicinity, Müller has found five species of Leptalis, of which only four are common and discussed by him. Of these four, Leptalis melia mimics nothing; all the other three_are imitative species, and mimic distinct groups of butterflies; Leptalis astynome, resembling a Heliconian-like Danaid, Mechanitis Lysimnia; another, which he calls Leptalis thalia, mimicking an Acræan, Ácræa thalia, so closely that Müller at first supposed it to be an Acrean;

and the last, Leptalis melite, bearing a close resemblance to the female of one of its own family, Leptoneura Lycinunia.-Buffalo Daily Courier, Aug. 25, 1876.

4. A Preliminary Note on Menopoma Alleghaniensis of Harlan; by A. R. GROTE, (Proc. Amer. Assoc., Buffalo, 1876.)-I have been able to examine nearly one hundred specimens of the Menopoma Alleghanense, the aquatic salamander living in the tributaries of the Mississippi, taken in the months of July and August in the Alleghany river, at Olean, N. Y. The object of the present communication is to record the fact that the more reddish unicolorous specimens, which have been described as a distinct species under the name of fuscum by Holbrook, and which are retained as a distinct species by Prof. Cope in his check list, cannot be considered as a different species from the spotted specimens from which the original description seems to be drawn. We have one species in the tributaries of the Ohio and Mississippi, and not two. The larger, and apparently often the female specimens, are referable to Holbrook's name. Between the two there seems to be all possible grades, and from the same locality, although the two extremes are more numerous, and, at first sight, readily picked out.

I have also to record the fact that the animal sheds a transparent membrane, which I believe is the exterior layer of the skin. While observing this fact in the aquarium of the Buffalo Society of Natural Sciences, Prof. S. W. Garman and myself were able to find an almost complete skin, all the feet and the toes being readily perceived while floating and unfolding it in the water. This same skin was observed at first gathered in the mouth of the animal, which was apparently in the act of swallowing it. This last observation is interesting, since a similar habit had been previously observed in the case of the common toad. All individuals of the Menopoma that I have observed have in the water an intermittent swaying motion from side to side. While I have not been able to verify the conjecture, this movement of the body may be connected with the effort of the animal to get rid of its skin. On the other hand it may be a movement to attract the sexes, or connected with the breeding period.

In Dactylethra and Cyclorhamphus Prof. Garman has observed a similar shedding of the skin. We may predict that the same thing occurs in the other more exclusively aquatic forms Necturus tetradactylus (Menobranchus lateralis of authors), Amphiuma, Siren, and also in the forms that take to the land, as Amblystoma, Plethodon, Desmognathus, and Diemyctylus, as well as in Megalobatrachus of Japan.

I have to record also the fact that females opened on August 21st, contained well developed eggs attached by a membrane to the ovary.

I finally wish to record the important fact that the eggs are deposited in August. (I exhibit one taken from the aquarium this morning, Aug. 30th, 1876.) The yolk is seen floating freely in a glairy fluid, enveloped in a membrane similar to that containing

the albumen in a bird's egg inside the shell. The eggs are laid in a connected string and impregnations probably occur as they are extruded. The egg takes in water by endosmosis.

The Menopoma frequents the muddy banks of the river, in which to secrete its eggs. In external appearance there is at this time a change, and we may say that the animal puts on its "marriage dress." The tail broadens and there is a plaited extension of the skin, along the sides of the body. The Menopoma is nocturnal in its habits.

5. The Entomological Section of the American Association, Buffalo, N. Y. Address of DR. LECONTE, President of the Section. After noticing some of the evidences of progress in new publications, etc., Dr. LeConte added:

I would gladly stop here, but a sense of duty to science, and my obligation to you alike forbid silence. I have to speak of a subject of a disagreeable nature.

It is concerning the efforts made by you and other members of the Association at the last meeting at Detroit, to procure the appointment of a Commission for the protection of Agriculture against noxious insects: this Commission to be composed of properly informed men of science, and chosen under such circumstances as would prevent the influence of political bias, or personal favoritism. If I do not fatigue your memory too much, you will recollect the memorials that were so extensively signed, in relation to this subject; copies of which memorials are again before you. These memorials were extensively circulated at the West, and were signed by many of the most influential bodies for the promotion and protection of agriculture in that region. During the winter these memorials were sent to Congress, in the expectation that some proper legislation would follow. One of the Senators, in fact, introduced a bill which seems to have been very carefully considered, and indeed bears upon its face some evidence of scientific guidance. This bill provided for the appointment of three Commissioners for five years: the Commissioners to be nominated by the Council of the National Academy of Sciences to the Secretary of the Interior. This bill, having been referred to the Committee on Agriculture, was returned so altered in form as to provide for one Commissioner, to be appointed by the Department of Agriculture, the very enemy and incubus from which the western agriculturists specially desired to be relieved.

The bill in this form passed the Senate, several of the members taking occasion in the discussion which preceded the passage, to talk to the demonstration of their own ignorance of the subject. However, this discussion has been already so severely commented upon in several of the newspapers of the Mississippi valley, that it is quite unnecessary for me to add anything farther, except the hope that the Legislature which chooses the successors of those Senators will have men of better education and higher intelligence offered to them as candidates for the position.-Buffalo Daily Courier, Aug. 25, 1876.