PANGENESIS. 175 



ment of the secondary characters proper to the sex 

 of the individual may be explained by a slight 

 difference in the elective affinity of the cells so that 

 they attract the corresponding gemmules rather than 

 those of the opposite sex, which as we have seen 

 are also present. 



The male characters of the male sex are in many 

 species latent except at certain seasons of the year, 

 and in both sexes the proper characters are latent 

 until sexual maturity. All such latent characters are 

 closely connected with the cases of ordinary reversion. 

 The appearance (whether seasonal or in the course of 

 development) of cells with affinities for the latent 

 gemmules explains the development of the characters 

 in question. 



Certain butterflies and plants {e.g. Lythrum) pro- 

 duce two or more separate forms of individuals. In 

 these cases each individual includes the latent gem- 

 mules of the other forms as well as its own. Her- 

 maphroditism in unisexual species, and especially in 

 the occasional cases of insects in which the right side 

 of the body is one sex and the left side the other, the 

 line of separation dividing the individual into two 

 equal halves, can be explained by slight abnormal 

 changes in the affinities of cells for gemmules, so 

 that a certain group of cells, or all the cells on one 

 side of the body, attract the gemmules which would 

 normally have remained latent. 



Reversion is induced by a change of conditions 

 and especially by crossing. The first results of crossing 



