Cunningham, Unisexual Inheritance. 5 



arise by changes in the determinants within the germ plasm, changes 

 which are independent of the condition of the soma. How then do 

 these modified determinants ever come to depend for their behaviour 

 on the condition of the soma? 



It is perhaps easy enough for the follower ofWeismaun to say 

 that the variation which arose in certain germ cells originally was 

 not merely production of determinants which would in development 

 produce antlers, but of determinants which would only produce antlers 

 when the body was in the condition caused by the activity of the re- 

 productive organs. But since the variations of the determinants in 

 the germ cells are supposed to be entirely independent of the soma 

 or its condition there is no reason why such a variation should ever 

 arise. The periosteum of the frontal bones, the formative action of 

 which produces the antlers, has not originally any sexual character, 

 is not in other animals specially affected by the periodical activity of 

 the generative organs. Why then should the variation in the deter- 

 minants which gives rise to antlers be correlated with the sexual 

 function ? 



It is I think impossible in this case to explain the facts by the 

 process of selection, for if the development of the antlers took place 

 like that of teeth at a certain stage of life independently of the sexual 

 functions, the antlers would be equally effective as weapons. A tiger 

 does not lose his teeth when castrated, what advantage then is it to 

 the deer tribe that the development of the antlers should be so pro- 

 foundly affected when the reproductive organs are removed? Selection 

 does not even explain the presence of antlers in deer and their absence 

 in other tribes of mammals, such as horses or swine. There is no 

 valid evidence, in spite of the fabled occurrence of horned horses, of 

 antlers occurring as occasional spontaneous variations, in animals that 

 do not normally possess them. 



Another important peculiarity of antlers is their annual loss and 

 recrescence. According to Weismann's conception the determinants 

 are used up when the cells which they determine have been definitely 

 formed. In his treatise on Das Keimplasma he expressly refers to 

 the antlers of stags in the chapter on regeneration, or as I prefer to 

 call it, recrescence. He believes that recrescence is not a process due 

 to a common original property of organisms, but is a special adaptation 

 produced by selection. This means that as an occasional variation 

 there occur in certain cells not merely the determinants of the cells 

 developed from them, but also extra sets of determinants which can 

 provide the regenerated tissues when the first are removed. The for- 

 mation of these extra or reserve determinants is supposed to occur in 

 the germ, as a blastogenic variation, and selection alone is supposed 

 to decide whether the possibility of recrescence shall belong to a given 



