4 Cunningham, Unisexual Inheritance. 



racters, and hands them on to the germ cells of the following gene- 

 ration, although the characters themselves do not actually show 

 themselves in the female. But more than this he points out is required. 

 The determinants exist also in the cells of the body of the female, 

 because in certain cases when the female has become sterile from old 

 age the male characters are developed. Conversely the determinants 

 of the female characters exist in the male, because when the latter is 

 castrated at an early age the male characters are not developed or, 

 asWeismann interprets the matter, female characters are developed 

 instead. Weismann's explanation of the facts then is that in each 

 rudiment of an organ in the developing soma there are two sets of 

 determinants or a set of double determinants, one set of which is active 

 and the other latent, while the latent may be called into activity by 

 special conditions such as castration, or sterility. 



But so far as I can discover Weismann has made no attempt 

 to explain how on his own theory the activity of one or other set of homo- 

 logous determinants in the soma, in an external organ for example, 

 can be in any way affected by the removal of the primary generative 

 organs, or by the condition of those organs. He conceives the deve- 

 lopment of the individual, as in the first place a subdivision of the 

 fertilised ovum into a number of cells, some of which will become the 

 germ cells of the next generation. The rest then are the somatic 

 cells, and these as they divide become differentiated, each cell as it 

 is formed taking with it only the determinants of the organ or organs 

 in whose formation it is going to take part. According to the theory 

 the fate of these somatic determinants can have no influence on the 

 determinants in the germ cells, for if they had we should have the 

 possibility of the inheritance of acquired characters. Consider then 

 the cells of the frontal bone in a young stag from which the antlers 

 will grow. These cells contain the determinants of the antler, and 

 presumably no female determinants, since the female possesses no 

 antlers. Yet if the testes are removed the determinants of the antlers 

 refuse to act, and remain latent. It is evident therefore that the 

 action of these determinants depends on the presence of the primary 

 generative organs, i. e. of the germ cells of the next generation, in 

 another part of the body. There must therefore be some connection, 

 some continuity between the germ cells and the determinants of the 

 antlers, while the theory postulates that there is none. 



It may perhaps be argued that the activity of the antler-determinants 

 depends not on the presence of the germ cells, but on nervous 

 excitement or other conditions of the soma, which are due to the 

 functional activities concerned in the liberation of the germ cells. In 

 that case how are we to conceive the origin of the variations which 

 originally gave rise to the antlers? Variations according to the theory 



