Imágenes de páginas

clusions with regard to the foot. This, he says, is to be distinguished very much earlier than has hitherto been recorded and, as one would naturally expect from Patten's study of Patella, which he quotes, it arises from a pair of folds and not from a single one as has generally been stated for related forms. In Succinea these two folds appear close behind the blastopore between the region of the mouth and anus, and approaching one another fuse in the median line forming an oval area. A median furrow persists for some time as evidence of the union as in Patella. This last fact gives some meaning to the similarly furrowed appearance occuring in Limnæus, Planorbis and Ancylus.

A study of over 100 embryo showed him that this paired origin is the rule, although examples were found where the elevation was unpaired, forming then a broad disc. In one apparently pathological case the blastopore had retained its supposed primitive elongated form and the beginning of the foot had the form of a horseshoe embracing its hinder end.

His conclusion that the foot represents the fused lips of the elongated blastopore removes the possibility of the organ being some kind of secondary formation, and makes it out to be a metamorphosed very ancient structure: and if the conclusion is correct, the molluscan foot is not quite such an anomalous structure as it has hitherto seemed.

A few remarks concerning the podocyst and the so called "Nackenblase are of interest in that they show that the latter structure is not an organ at all, and that the contracting motions that have been observed in it are due to the contractions of the podocyst which acts as an organ of circulation. For in Succinea where the structure in question has an enormous development and where no podocyst occurs there are no such movements to be seen. The structure is, he says, a mass of endoderm cells swollen with albumen, the embryonal liver and the outer body epithelium.

With regard to the shell gland, Schmidt substantiates, in the main, the early observations of Gegenbaur or Clausilia and shows Korschelt's doubt concerning them to be unfounded. A large series of Clausilia embryos gave ample opportunities for study, and as a result it appears that very early the shell gland arises as an invagination of the outer epithelium, and closing up, becomes completely cut off from its parent layer. Sections show it to be completely surrounded by mesoderm. The hollow vesicle thus formed becomes flattened out so that he distinguishes in it an outer and an inner layer of cells separated by a narrow space. The outer layer remains more or less un

changed, but the cells of the inner one proliferate and begin to lay down the shell, which may be distinguished 'in sections as a very thin lamina. At about this time observations of embryos by reflected light show a small invagination or hole near the center of the newly formed shell, which is thus laid bare. The hole then is of secondary formation and not, as Korschelt supposes, something that has persisted from the original invagination.

It appears then that the internal formation of the shell, as it has been generally recognized in the so called naked pulmonates is not an exception to a rule but the rule itself, and that the condition obtaining in Limax and others differs from that in the rest of the pulmonates only in so far as a rudimentary condition is retained in the adult animal.-F. C. KENYON, Ph. D., Clark University, Worcester, Mass.


Physical and Social Heredity.-The great courtesy of the Editor of this journal in reprinting one of my paper from Science preliminary to replying to it encourages me to ask him for a page or two of comment on his reply. This is the more needful since the second of my papers which he criticises may not have been seen by the readers of the NATURALIST, and the third has only just appeared in Science, (March 20 and April 10, 1896).

The main question at issue is the relation of consciousness or intelligence to heredity; the other matter, that of the relation of consciousness to the brain, being so purely speculative that I shall merely touch upon it at the end of this note.

Prof. Cope' says: "there is no way short of supernatural revelation by which mental education can be accomplished other than by contact with the environment through sense-impressions, and by transmission of the results to subsequent generations. The injection of consciousness into the process does not alter the case, but adds a factor which necessitates the progressive character of evolution." Both of these sentences I fully accept, except that the word "transmission" seem to imply the Lamarkian factor, which I think the presence of consciousness renders unnecessary. Using the more neutral word" conservation" instead of "transmission," I may refer to three points on which Prof. Cope criticises my views: first, conservation of intelligent acquisitions from genera1 AMER. NAT., April, 1896, p. 343.

tion to generation; second, "the progressive character of evolution;" and third, "mental education" or acquisition.


First, agreeing as we do on the fact of mental acquisition or selection through pleasure, pain, experience, association, etc.," Prof. Cope cites my second paper (Science, Mar. 20th) in which I hold that consciousness makes acquisitions of new movements by such selections. He then says, if so, then I admit the Lamarkian factor. But not at all; it is just the point of my article to refute Romanes by showing that adaptation by intelligent selection makes the Lamarkian factor unnecessary. And in this way, i. e., this sort of adaptation on the part of a creature keeps that creature alive by supplementing his reflex and instinctive actions, so prevents the operation of natural selection in his case, and gives the species time to get congenital variations in the lines that have thus proved to be useful (see cases cited). Farthermore, all the resources of Social Heredity-the handing down of intelligent acquisition by maternal instruction, imitation, gregarious life, etc.-come in directly to take the place of the physical inheritance of such adaptations. This influence Prof. Cope, I am glad to see, admits; although in admitting it, he does not seem to see that he is practically throwing away the Lamarkian factor. For instead of limiting this influence to human progress, we have to extend it to all animals with gregarious and family life, to all creatures that have any ability to imitate, and finally to all animals which have consciousness sufficient to enable then to make conscious adaptations themselves: for such creatures will have children that do the same, and it is unnecessary to say that the children must inherit what their fathers did by intelligence, when they can do the same things by their own intelligence. As a matter of fact Prof. Cope is exactly the biologist to whose Lamarkism this admission is, so far as I can see, absolutely fatal; for he more than all others holds that adaptations all through the biological scale are secured by consciousness. If so, then he is just the man who is obliged to extend to the utmost the possibility of the transmission also of these adaptations by intelligence, which, as I said, rules out the need of their transmission by physical heredity. At any rate he is quite incorrect in saying that "he [I] both admit and deny Lamarkism."

To this argument of mine Prof. Cope presents no objection that I see except one from analogy. He says: "I do not see how promiscuous variation and natural selection alone can result in progressive psychic evolution, more than in structural evolution, since the former is condi2 And in this I think he is right: see chaps. VII and IX of my Mental Development (Macmillans, 2d. ed.).

tioned by the latter."

As to the word "progressive," I take up that question below; but as to the analogy with structural evolution, two auswers occur to me. In the first place, Prof. Cope is, as I said, the very man who holds that all structural evolution is secured by direct conscious adaptations. He says: "mind determines movements and movements have determined structure or form." If this be true how can psychic be conditioned by structural evolution? Would not rather the structural changes depend upon the psychic ability of the creature to effect adaptations? And then, second, at this point Prof. Cope assumes the Lamarkian factor in structural evolution. Later on he makes the same assumption when he says: "But since the biologists have generally repudiated Weismannism," etc. This is a curious saying; for my impression is that even on the purely biological side, the tendency is the other way. Lloyd Morgan has pretty well come over; Romanes took back before he died many of his arguments in favor of the Lamarkian factor; and here comes a paleontologist, Prof. Osborn, -if he is correctly reported in Science, April 3rd, p. 530-to argue against Prof. Cope on this very point with very much the same sort of argument as this which I have made. And while Prof. Cope will agree with me that this sort of argumentum ex autoritate is not very convincing, yet he will not object to my balancing off his dictum with the following from a letter which just comes to me from another distinguished biologist, Prof. Minot: Neo-Lamarkism seems to me an impossible

[ocr errors]


But Prof. Cope goes on to say that I " both admit and deny Weismannism;" on the ground that "his [my] denial of inheritance only covers

3 Since writing this I have heard Prof. Osborn read a paper which confirms the agreement between him and me which I supported in the text above. I reached my conclusion independently and one of my Science articles gives report of it as expressed in a criticism of Romanes before the New York Academy of Science on Jan. 31st, 1896. Prof. Osborn's expression "ontogenic variations" i. e. those brought out by "environment (which includes all the atmospheric, chemical, nutritive, motor, and psychical circumstances under which the animal is reared)" seems to make these adaptations after all constitutional. As Prof. Osborn says

this will not do for all cases; and I think it will not do for instinct, where constitutional variations without the aid of intelligence would never suffice (as Romanes says) to keep the animal alive while correlated variations are being perfected phylogenically. But it seems to answer perfectly where intelligent or other adaptations supplement the constitutional variations—and that is just the point made in my Science paper. As to the way these ontogenic variations or adaptations are brought about in the individual creature, see the remarks on "organic selection" below. I am printing in the next issue of this journal (June) a full statement of the entire position.

the case of psychological sports." But I do not see the connection. If Prof. Cope means denial of the inheritance of acquired characters then I deny it equally of sports and other creatures; but I do not deny that the native "sportiveness" (!) of sports tends to be transmitted. In my view the "massiveness of front" which progress shows (and which Prof. Cope accepts) shows that in social transmission the individual is usually swamped in the general movement as the individual sport is in biological progress. As a matter of fact, however, the analogy from "sports" which Prof. Cope makes does not strictly hold. For the social sport, the genius, is sometimes just the controlling factor in social evolution. And this is another proof that the means of transmission of intelligent adaptations is not physical heredity alone, but that they are socially handed down. I do not see, therefore, what Prof. Cope means by saying that I "admit and deny Weismannism," for I have never discussed Weismannism at all. I believe in the Neo-Darwinian position plus some way of getting "determinate variations." And for this latter I think the way now suggested is better than the Lamarkian Like many of the biologists (e. g., Minot) I see no proof of Weismannism (just as I protest mildly against being sorted with Mr. Benjamin Kidd!); yet I have no competence for such purely biological speculations as those which deal in plasms!


Second, the question as to how evolution can be made "progressive." Prof. Cope thinks only by the theory of "lapsed intelligence" or “inherited habit." Admitting that the intelligence makes selections, then they must be inherited, in order that the progress of evolution may set the way the intelligence selects. But suppose we admit intelligent selection (even in the way Prof. Cope believes); still there are two influences at work to keep the direction which the intelligence selects apart from the supposed direct inheritance. There is that of social handing down, imitation, etc., or Social Heredity, which I have already pointed out; and besides there is the survival by natural selection of those creatures which have variations which intelligence can use. This puts a premium on these variations and their intelligent use in following generations. Suppose, for instance, a set of young animals some of which have variations which intelligence can use for a particular adaptation, thus keeping these individuals alive, while the others who have not these variations die off; then the next generation will not only have the same variations which intelligence can use in the same way, but will also have the intelligence to use the variations in the same way, and the result will be about the same as if the second generation had inherited the adaptations directly. The direc

« AnteriorContinuar »