HEREDITY OF SEX 279 



inherited as a Mendelian factor, in some cases female- 

 ness, in others maleness, being due to the presence of a 

 factor which is absent in the other sex; and the whole 

 category of characters which have sex-limited trans- 

 mission appears to be only a special case of gametic 

 coupling, due, if the chromosome theory is correct, to 

 the association of the factors for sex-limited char- 

 acters and for sex itself in the same chromosome.] 



By way of further illustrating the far-reaching im- 

 portance of the information which has been rendered 

 available by the combined use of experimental and 

 cytological methods, we may here briefly criticise the 

 celebrated theory of inheritance put forward by Weis- 

 mann in 1892 under the name of the * Germ-Plasm 

 Theory.' Some notice of this theory, which might 

 otherwise have been permitted to go the way of similar 

 valuable provisional hypotheses, is rendered almost 

 necessary by the circumstance of its having been 

 revived in a prominent manner in the English transla- 

 tion of Weismann's book, ' The Evolution Theory.' 

 In this book, published in 1904, the bearing of the 

 Mendelian evidence upon the subject of inheritance is 

 practically ignored ; although, in the face of the definite 

 experimental information now rendered available, 

 biologists are beginning to realize that the circum- 

 stantial evidence, formerly so much relied upon, will 

 in future constitute a much less prominent feature in 

 these discussions. 



Weismann's theory of inheritance, and the Theory 

 of Ancestral Heredity in its original form, are based 



