June 29, 1905] 



NA TURE 



Chapters on reproduction and the process of fertil- 

 isation in both unicellular and multicellular organisms 

 lead us on to a copious exposition of' the author's 

 theory of the germ-plasm and its constitution, with 

 the building up of the assumed ultimate vital units or 

 " biophors " into the successive complexes of " deter- 

 minants," "ids," and "idants." After a discussion 

 of the facts brought to light bv the labours of the 

 " Entwicklungsmechanik " school, and a fairly full 

 notice of recent work on regeneration in its relation 

 to the germ-p!asm hypothesis, we come to what is 

 in many respects the strongest part of the book, the 

 refutation, namely, of the Lamarckian view of the 

 transniissibility of functional modifications. 

 Here Weismann has always been at his best, 

 and to him undoubtedly belongs the credit 

 of having awakened and sustained so fresh 

 and vigorous a body of opinion in reference 

 to this point as virtually to have created one 

 of the most important epochs in the history 

 of evolutionary doctrine. The two ne.xt 

 chapters deal with the author's hypothesis of 

 " germinal .selection," as to which it may be 

 sufficient to remark that, however ingenious 

 and interesting the theory may be as an 

 .ittompt to explain the chief phenomena of 

 variation, it is as yet far from having reached 

 the stage of verification. In the succeeding 

 chapters, which deal with inbreeding, par- 

 thenogenesis, and reproduction, both sexual 

 and asexual, it is interesting to observe that 

 Weismann has considerably modified his 

 standpoint with reference to amphimixis, his 

 present view approximating in some degree 

 to that advanced several years ago by Ha\- 

 craft. This section is preceded by a discus- 

 sion of the " biogenetic law " of Haeckel, 

 and is followed up by chapters on the in- 

 fluence of the environment and of isolation 

 in the formation of the specific type, together 

 with the various causes of extinction. 



The book concludes with some theoretical 

 considerations on the subject of spon- 

 taneous generation, and a final vindica- 

 tion of the principle of selection, the 

 dominance of which principle over all the 

 categories of vital units may be taken as the 

 key-note of the entire treatise. 



it will be seen that the ground covered by 

 this work is very extensi\'e. Though most 

 of the topics dealt with are considered by 

 the author chiefly or solely with an eye to 

 his theory, his treatment never lacks in- 

 terest, and the result is worthy of his high 

 reputation. There are some points as to 

 which we should have welcomed a more 

 thorough discussion, and others on which we 

 confess to remaining unconvinced for reasons 

 quas nunc perscribere longutn est; but it 

 would be ungrateful not to acknowledge to 

 the full the immense services rendered to biological 

 science by the stimulating labours in the domain both 

 of theory and practice of which this book is a 

 monument. 



The illustrations are for the most part excellent. 

 Of the two here reproduced, the first serves to illus- 

 trate the basis of one of the chief arguments brought 

 forward bv Weismann, as also by Strasburger and 

 O. Hertvvig, in favour of regarding the nuclear 

 chromatin as the true hereditary substance, viz. the 

 numerical equality of the chromosomes and the dis- 

 parity in amount of the cell-protoplasm in the 

 generative products of the two sexes. The second 

 (from Fischer) supplies evidence of the possibility of 



NO. l8t I, \0L. 72] 



certain external conditions, in this case temperature, 

 influencing the germ-plasm even while contained 

 within the body of the parent. 



We ha\-e little space left for detailed criticism, but 

 must point out that by some unaccountable oversight 

 the letterpress of plates i. and ii. contains several 

 serious errors — patent at once to the trained entom- 

 ologist, but calculated to mislead the general reader. 

 These mistakes appear uncorrected in the English 

 translation, where also, as if to make confusion 

 worse confounded, "die folgende Art" (plate ii.. 

 Fig. 20) is rendered " the foregoing species." For- 

 tunatelv however the lapses in question are not of 



of fertii: 

 second polar body ; s/f, spermatozi( 

 eeg-protoplasm is meeting it : J-Sii\ reduC' 

 of spermatozoon : <J i', 9 A-, sperm nuci 

 chromosomes (c/iy) ; only the male nucleus 

 has already divided into two : /~sfi, segi 

 " Evolution Theory." Translated by Prof. 



two chromo 



d nucleus of l\v 



nd Mrs. Tho 



Rk 2, first and 

 protrusion of the 

 im ; spk, nucleus 

 vum nucleus, each with two 

 trosphere {c</'h), which in C 

 pindle. From 



a nature to impair the value of the argument which 

 the figures are meant to illustrate. 



Other slips in the translation are plainly due to 

 the fact that the translators are unfamiliar with por- 

 tions of the subject-matter, as in vol. ii., p. 348, 

 where the point of the argument is blunted by the 

 rendering of " Xachtfalter " as "butterfly"; such 

 imperfections, though they should be remedied in a 

 new edition, are of little real importance. More 

 serious is a mistranslation, or perhaps a misprint 

 (vol. i., p. 290) by which the words of the original, 

 " in welchem die eigentliche Chromatinsubstanz nur 

 in vielfacher Zertheilung enthalten ist," are perverted 

 into a statement which is almost grotesquely incorrect. 



