The Laws of Heredity. 1 79 



Paternal Line Maternal Line 



First Generation Grandfather Grandmother Grandfather Grandmother 



Second Generation 



father mother 



Third Generation son daughter ^ son daughter 



If we compare this table with that given above for the salpae, it 

 is impossible not to be struck with the resemblance. 



But a difficulty still remains. In cases of reversional heredity 

 where the grandson resembles the grandfather, the grandnephew 

 the granduncle the intermediate stages being totally unlike either 

 how is this resemblance to be explained ? Above all, how can 

 it be said, as we have done, that these cases are to be referred to 

 immediate heredity ? The reply to this question is to be found in 

 one of two hypotheses ; either these resemblances are fortuitous, 

 or else they have been preserved in the latent state by the inter- 

 mediate generations, and thus what appears to be mediate heredity 

 is really immediate. The first hypothesis cannot be accepted, 

 therefore we must hold the second. And this leads us to ask 

 what is meant by ' latent characters. 1 



One of the best examples of these, says Darwin, is afforded 

 by secondary sexual characters. In every female all the secondary 

 male characters, and in every male all the secondary female cha- 

 racters exist in a latent state, ready to be evolved under certain 

 conditions. It is well-known that a large number of female birds 

 when old or diseased, or when operated on, partly assume the 

 secondary male characters of their species. Waterton gives a 

 curious case of a hen which had ceased laying, and had assumed 

 the plumage, voice, spurs, and warlike disposition of the cock ; 

 when opposed to an enemy she would erect her huckles and show 

 fight. Thus every character, even to the instinct and manner of 

 fighting, must have lain dormant in this hen as long as her ovaria 

 continued to act. We see something of an analogous nature in 

 the human species. 



On the other hand, with male animals, it is notorious that the 

 secondary sexual characters are more or less lost when they are 

 subjected to castration, as in the case of capons. 



Thus the secondary characters of each sex lie dormant in the 



