27, costatus, var-"

29,

Doto coronata? young showing the oval shell and the swimming organ or velum from above. V, velum, y, eyes, p, operculum, the hinged disk used in closing the opening of the shell when the velum and foot, k, are drawn into it as the animal retracts The mouth is indicated by the black spot near the center of the velum.

30, View of the same taken partly from the side.

7. Cavolina, dorsal view (after Brown).

8, Helix, seen partly from the under side.

** 9, The same with the shell dissolved by acid, showing the conical bag of the mantle partly unwound.

a broken specimen winding about on a shell of Lima.

11, Patella, diagram showing relation of shell to the crawling disk.

12, Same, edge of shell in section, and mantle exposed on one side.

13, Oyster in natural position attached firmly to a stone, but projecting without other support for about of its own length,

14, Clam shell (Mya) in outline above an oyster shell and both in the same position with reference to the structure of the two animals, if these were in their places inside of the shell. 15, Mytilus edulis (after Morse), common mussel attached to a stone by its byssus with the foot protruded.

16, Lima, view from the posterior end, showing bilateral symmetry.

Common clam seen from the side with the siphon and mantle-rim or foot

19, Mulleria, right or attached valve, with the solidified beak and the young shell showing at the

end of the beak (after Adams).

20, Beak of the same showing the form of the young shells, from the dorsal side.

21, Pl. oxystomus, var. revertens, spiral showing the unwinding in an adult individual, due to disease.

714. Top view of Fig. 21, and showing also the nucleus or young shell.

22,

Pl. oxystomus, extremely old specimen showing similar unwinding of the spiral due to the weakness of senility.

23, Magilus antiquus, showing the regular spiral below and the irregular straight shell above built after the spiral shell has been buried in the coral (after Woodward).

24, Pl. steinheimensis, var. æquiumbilicatus, view of section showing how perfectly balanced the two sides of the spire are in some shells during their entire growth.

25, External view of the same shell, seen from the ventral side.

26, Anomia, young shell, left valve (after Morse).

28, Anomia, young shell, right valve after the shell is turned so as to rest on this valve, which is now below and is making an effort to readjust the lateral symmetry by the geomalic growth of this valve around the byssal plug (aftor Morse).

29, The same, with the same valve after it has been built around the byssal plug (after Morse).

30, Anomia glabra, a full-grown shell, seen from the lower, right side, with upper left valve showing its projecting edges and beak beyond.

31. The same from the upper or left side, lower shell necessarily concealed.

32, The same from the anterior end to show distortion produced by the change in position. The lower or right valve is too concave to be visible.

[All figures not otherwise designated are original.]

ON ARCHÆSTHETISM.

BY E. D. COPE.

I. THE HYPOTHESIS OF USE AND EFFORT.

HE claims of the theory of Lamarck, that use modifies struc

THE

ture in the animal kingdom, are being more carefully considered than heretofore, and are being admitted in quarters where they have been hitherto neglected or ignored. Eleven years ago I restated the question as follows:1

"The influences and forces which have operated to produce the type structures of the animal kingdom have been plainly of two kinds 1. Originative, 2. Directive. The prime importance of the former is obvious; that the latter is only secondary in the order of time or succession, is evident from the fact that it controls the preservation or destruction of the results or creations of the first.

“Wallace and Darwin have propounded as the cause of modification in descent their law of natural selection. This law has been epitomized by Spencer as the survival of the fittest.' This neat expression no doubt covers the case, but it leaves the origin of the fittest entirely untouched. Darwin assumes a 'tendency to variation' in nature, and it is plainly necessary to do this, in order that materials for the exercise of a selection should exist. Darwin and Wallace's law is, then, only restrictive, directive, conservative or destructive of something already created. I propose then to seek for the originative laws by which these subjects are furnished-in other words, for the causes of the origin of the fittest.

"It has seemed to the author so clear from the first as to require no demonstration, that natural selection includes no actively progressive principle whatever; that it must first wait for the development of variation, and then after securing the survival of the best, wait again for the best to project its own variations for selection. In the question as to whether the latter are any better or worse than the characters of the parent, natural selection in no wise concerns itself."

In seeking for the causes of the origin of variation, the following hypothesis was proposed:

"What are the influences locating growth force? The only efficient ones with which we are acquainted, are, first, physical and chemical causes; second, use; and I would add a third, viz: effort. I leave the first as not especially prominent in the economy of type growth among animals, and confine myself to the 1 The Method of Creation, 1871, pp. 2 and 18. Walker Prize Essay. Proceeds. Amer. Philos. Soc., pp. 230-246.

two following. The effects of use are well known. We cannot use a muscle without increasing its bulk; we cannot long use the teeth in mastication without inducing a renewed deposit of dentine within the pulp-cavity to meet the encroachments of attrition. The hands of the laborer are always larger than those of men of other pursuits. Pathology furnishes us with a host of hypertrophies, exostoses, etc., produced by excessive use, or necessity for increased means of performing excessive work. The tendency, then, induced by use in the parent, is to add segments or cells to the organ used. Use thus determines the locality of new repetitions of parts already existing, and determines an increase of growth force at the same time, by the increase of food always accompanying increase of work done, in every animal. "But supposing there be no part or organ to use. Such must have been the condition of every animal prior to the appearance of an additional digit or limb or other useful element. It appears to me that the cause of the determination of growth force is not merely the irritation of the part or organ used by contact with the objects of its use. This would seem to be the remote cause of the deposit of dentine in the used tooth; in the thickening epidermis of the hand of the laborer; in the wandering of the lymph-cells to the scarified cornea of the frog in Cohnheim's experiment. You cannot rub the sclerotica of the eye without producing an expansion of the capillary arteries and corresponding increase in the amount of nutritive fluid. But the case may be different in the muscles and other organs (as the pigment cells of reptiles and fishes) which are under the control of the volition of the animal. Here, and in many other instances which might be cited, it cannot be asserted that the nutrition of use is not under the direct control of the will through the mediation of nerve force. Therefore I am disposed to believe that growth force may be, through the motive force of the animal, as readily determined to a locality where an executive organ does not exist, as to the first segment or cell of such an organ already commenced, and that therefore effort is, in the order of time, the first factor in acceleration."

A difficulty in the way of this hypothesis, is the frequently unyielding character of the structures of adult animals, and the difficulty of bringing sufficient pressure to bear on them without destroying life. But in fact the modifications must, in most instances take place during the period of growth. It is well known that the mental characteristics of the father are transmitted through the spermatozoõid, and that therefore the molecular movements which produce the mechanism of such mental characters, must exist in the spermatozoöid. But the material of the spermatozoõid is combined with that of the ovum, and the em

bryo is composed of the united contents of both bodies. In a wonderful way the embryo develops into a being which resembles one or both parents in minute details. This result is evidently determined by the molecular and dynamic character of the original reproductive cells, which necessarily communi-. cate their properties to the embryo, which is produced by their subdivision. Rud. Hering has identified this property of the original cells with the faculty of memory. This is a brilliant thought, and, under restriction, probably correct. The sensations of persons who have suffered amputation, shows that their sensorium retains a picture or map of the body so far as regards the location of all its sensitive regions. This simulacrum is invaded by consciousness whenever the proper stimulus is applied, and the locality of the stimulus fixed by it. This picture probably resides in many of the cells both sensory and motor, and it doubtless does so in the few cells of simple and low forms of life. The spermatozoöid is such a cell, and, how or why we know not, also contains such an arrangement of its contents, and contains and communicates such a type of force. It is probable that in the brain cell this is the condition of memory of locality. If now an intense and long-continued pressure of stimulus produces an unconscious picture of some organ of the body in the mind, there is reason to suppose that the energies communicated to the embryo by the spermatozoõid and ovum, will partake of the character of the memory thus created. The only reason why the oft-repeated stories of birth-marks are so often untrue, is because the effect of temporary impressions on the mother is not strong enough to counterbalance the molecular structure established by impressions oftener repeated throughout much longer periods of time.

The demonstration of the truth or falsity of this position so as to constitute it the true doctrine of evolution, could only be veri fied from the prosecution of the science of palæontology. It is only in this field that the consecutive series of structures can be obtained, which show the directions in which modification has taken place, and thus furnish evidence as to the causes of change. The most complete result of these investigations up to the present time, has been the obtaining of sufficiently full series of the Mammalia of the Tertiary period, to show their lines of descent. In this way the series of modifications of their teeth and feet has

been discovered, and the homologies of their parts been ascertained. Perhaps the most important result of these investigations is the following: The variations from which natural selection has derived the persistent types of life, have not been general or even very extensive. They have been in a limited number of directions, and the most of these have been towards the increase in perfection of some machine. They bear the impress of the presence of an adequate originating cause, directed to a special end. Some of the lines struck out have been apparently inadequate to cope with their environment, and have been discontinued. Others have been more successful and have remained, and attained further modification.

* *

The reader can estimate the chance of the production of an especially adaptive mechanism in the absence of any pressure of force directing growth to that end. It appears to me that the probability of such variation appearing under such circumstances is very slight indeed, and its continuance through many geologic ages directed to the perfecting of one and the same machine, still smaller. For this reason, attempts have been made to demonstrate a mechanical cause for the modifications of structure observed. For these I refer to papers by Messrs. Alpheus Hyatt, J. A. Ryder and myself; by Professor Hyatt "Upon the effects of gravity on the forms of shells and animals;" Mr. Ryder "On the mechanical genesis of Tooth Forms ;" and "On the laws of digital reduction;" by myself "On the origin of the specialized teeth of the Carnivora;" "On the origin of the foot structures of the Ungulates;" "On the effect of Impacts and Strains on the Feet of Mammalia." Now demonstration of the mechanical effects of the application of force to matter can only be obtained by observation of the process, and this cannot be seen, of course, by the observation of fossils. The 1 Homologies and Origin of the Molar teeth of the Mammalia educabilia. Journal Academy Nat. Sciences, Philadelphia, March, 1874. Proceedings Academy Nat. Sci., 1865, p. 22.

'See Hyatt on this point, Tertiary Planorbis of Steinheim. Anniv. Mem. Bost.. Soc. Nat. Hist., 1880, p. 20.

* Proceeds. Amer. Assoc. Adv. Science, 1880, p. 527.

*Proceedings Academy Philadelphia, 1878, p. 45, 1879, 47.