The Evidence from Sexual Characters. 167 







confined to males are more variable than parts confined 

 to females; for variation in any part is due to inherit- 

 ance of a gemmule from the corresponding part of one 

 parent or the other, but when -the part is found in only 

 one parent the gemmule must come from that parent. 



As transmission of gemmules by the mother is more 

 rare than transmission by the father, it is plain that 

 parts which are confined to the male should be expected 

 to vary more than parts found in the female alone. 



Finally we should expect the male body as a whole to 

 be more variable than the female body, for the same 

 reason. 



In most cases it is impossible to trace any particular 

 variation back to its first appearance. This is almost 

 out of the question with wild animals, and most do- 

 mesticated races have been formed so slowly that it is 

 impossible to %iy whether the successive steps appeared 

 in males or in females, nor can we be sure that a varia- 

 tion is new when it first attracts attention. Still it is 

 interesting to note that the sudden variation which re- 

 sulted in the ancon breed of sheep was first noticed in a 

 male, although it is, of course, impossible to say whether 

 it was due to inheritance of gemmules from the father 

 rather than from the mother. Certain hereditary dis- 

 eases and montrosities, such as albinism or polydactyl- 

 ism, are fully as often traceable to a male origin as they 

 are to a female origin, but as we know that peculiari- 

 ties of this kind frequently skip a generation or two, we 

 can never be sure that we have traced them to their 

 origin. 



In the secondary sexual characters of animals we have 

 a class of phenomena which are not rare and exceptional, 

 for they are numbered by hundreds of thousands, and 

 they can be observed and studied by every one. 



