Weismannism tip to date (1893). I2 5 



chromosomes — even assuming that chromosomes are 

 the visible repositories of the carriers of heredity *. 



Referring the reader to Weismann's own exposition 

 for a full account of these and many others additions 

 to his general theory of germ-plasm, I will at once 

 proceed to consider the alterations or emendations of 

 that theory which have been published in his last two 

 volumes, and which, as we shall find, have in large 

 measure anticipated some of the most important points 

 in the foregoing criticism. Therefore in the following 

 criticism I will consider seriatim what he has now said 

 touching all these points, and conclude by offering 

 some general remarks on the resulting position of his 

 general system of theories up to the present date. 



Pursuing the same method of criticism as that 

 adopted in the preceding chapters, we will first con- 

 sider the further modifications of Weismann's theory 

 of heredity, and next those of his theory of organic 

 evolution. 



Weismanris tlieory of Heredity (1893). 



First of all, Weismann has now profoundly modified 

 his theory of polar bodies. For, owing to certain 

 more recent researches of Professor O. Hertwig, he 

 very candidly allows : — " My previous interpretation 

 of the first polar body as the removal of ovogenetic 

 nucleo-plasm from the egg must fall to the ground : 

 about this there is no possible doubt 2 ." 



1 It must always be remembered that the view adopted by Weismann 

 touching the nucleus (and more especially the chromosomes) of a germ- 

 cell being the sole seat of heredity, is still far from having been estab- 

 lished. 



2 Essays, vol. ii. p. 122. 



