NATURE 



'93 



THURSDAY, JANUARY 2, 15 



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THE INHERITANCE OF "ACQUIRED" 



CHARACTERS. 



Siir la Transtnissibilili' de Characteres acquis. By 



Eugenio Rignano. Pp. 320. (Paris : F. Alcan, 



1906.) Price 5 francs. 

 A MAN of science to command general attention 

 •^ »■ and interest must do two things ; first, he must 

 make interesting discoveries or profound generalisa- 

 tions ; and, secondly, he must do these things at the 

 right time. Darwin made his name because he ful- 

 filled both these conditions. Mendel died an unknown 

 man because he did not fulfil the second. He was 

 forty years too soon. Supposing that Mendel's paper 

 had been completely lost sight of, as it actually was 

 for thirty-five years, and very nearly was altogether, 

 his results must, sooner or later, have been obtained 

 by somebody else, who would then have won the 

 laurels which now belong to Mendel, not because he 

 made a greater discovery than Mendel, but because 

 he made it at a time when the state of biological 

 thought was such that it could appreciate the signifi- 

 cance of the discovery. 



If it is possibly fatal to make discoveries too soon, 

 it is certainly fatal to make them too late. It is 

 therefore with a certain .sense of weariness, mingled 

 with surprise, that we note the appearance of a 

 work on the transmission of acquired characters. 

 Lamarck's theory of evolution involved a belief in 

 the thesis that acquired characters are transmitted. 

 Darwin believed that evolution was due to the natural 

 selection of both innate and acquired characters, and 

 his theory of pangenesis was more than anything else 

 :v.i attempt (shirked by Lamarck) to provide a hypo- 

 thesis to account for the transmission of acquirements. 

 Darwin's suggestion that innate characters plaved a 

 part in evolution as well as acquired ones paved the 

 way for the great step taken by Weismann, who in 

 his theory of the continuity of the germ-plasm laid 

 the foundation of the modern, and still infant, science 

 of heredity by doing away with the transmission of 

 acquirements once and for all. 



The step taken liy Weismann is far and away th<' 

 iTiost important in the history of evolution, or at any 

 rate of genetics, because it divides that history into 

 two periods, in the first of which the problem to be 

 solved was : " How do the characters of an organism 

 get into the germ-cell which it produces?" whilst 

 in the second the problem has become : " How are 

 the characters of an organism represented in the germ- 

 cell which produces it? " 



Weismann showed that the problem of the first 

 period was as unreal as the question about the apple 

 dumpling which puzzled one of the Georges, by 

 opening our eyes to the fact that the characters of an 

 organism do not get into its germ-cells any more 

 than the apple gets into its crust, but that both the 

 germ-cells and the apple were there all the time. 



Darwin, although he made a great step in advance 

 of Lamarck by elaborating a theorv of evolution which 

 did not rest solely or even largely on the transmission 



NO. 1992, VOL. yy] 



of acquirements, did not go to the length of throwing 

 that theory overboard altogether. It was left for 

 Weismann to do this and thereby rid biology of a 

 belief which has been the occasion of more futile dis- 

 cussion than any other that can be named. The full 

 significance of Weismann 's action is seldom appre- 

 ciated, and cannot be done justice to here, but it is 

 not too much to say that without it the problem ol 

 heredity would have been doomed to insolubility, and, 

 to take a concrete example, that the Mendelian work 

 of the last seven years would have been impossible. 



Whether it is due to the general truth that a view 

 once widely held is difficult to stamp out, or whether 

 it is that there is something peculiarly fascinating in 

 the belief that acquired characters are transmitted, 

 the fact remains that there are still to be found isolated 

 biologists and whole hosts of medical men who still 

 hold it. However, as a belief in telegony, though 

 rare, still exists, we perhaps ought not to be surprised 

 al anything. 



The author of the book before us, who is an 

 engineer interested in sociology, believes in the trans- 

 mission of acquirements, and has invented a theory 

 of centro-epigenesis to account for the phenomenon. 

 If the book is read it must be read in conjunction 

 with the appendix dealing with this topic in Mr. 

 .-Xrchdall Reid's " Principles of Heredity," and with 

 Weismann's " Deszendenztheorie," which has been 

 translated into English bv Prof. J. Arthur Thomson. 



A. D. D. 



PROBLEMS OF VISION. 

 Zur zergleichenden Physiologic des Gesichtssiiuics. 

 By Prof. E. Raehlmann. Pp. iv + sS. (Jena: 

 G. Fischer.) Price 1.50 marks. 



THIS short pamphlet contains a discussion of three 

 interesting problems in vision. It has long 

 been known that the arrangement of the retinal 

 elements in regard to the light falling upon the eye 

 is reversed in the vertebrata and some invertebrates 

 as compared with the majority of the latter. The 

 author wishes to direct attention to the problem of 

 explaining how in these " inverted eyes " the stimulus 

 of light affects the retina. He puts forward the view 

 that the morphologically outer end of the rods and 

 cones acts in these cases as a reflector, and causes the 

 light to re-enter the inner limb where the visual 

 stimulus conmiences. In that sense, therefore, the 

 vertebrate retina is no exception to the general state- 

 ment that the rods always face the effective light rays. 

 The isolation of the rods by pigment leads the author 

 to an interesting account of the various forms of iris 

 and of retinal pigments. 



The second problem is the function of the tapetum. 

 The significance of this brilliant structure has received 

 little attention. Hatscliek has attempted to show that 

 it reinforces the incident light. The author, how- 

 ever, proceeds to show that the incident light is not 

 effective even partially, but that it is the rays reflected 

 from the concave and asymmetrical tapetal mirror 

 which illuminate the inner portion of the peripheral 

 retina. This area, weak in perception of detail, but 



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