114 PETER OKKELBERG 



sexual characters or the accessory reproductive organs, since 

 there are none in the larval stages of the lamprey. In insects 

 the secondary sex characters appear to be unaffected by the pres- 

 ence or absence of the sex glands, but in most other forms the 

 appearance of the secondary sexual characters may be the result 

 of certain hormones which are produced by the predominating 

 primary sex elements. This appears to be the case in the lam- 

 prey. Sooner or later in the life of the individual the male- or 

 the female-producing enzyme, if such it be, takes the lead so 

 that the action of the opposite enzyme is more and more sup- 

 pressed. The male or the female germ gland, which develops 

 as a consequence of the stronger enzyme, is capable of producing 

 certain hormones which, both at and after metamorphosis, cause 

 the secondary characters to appear. 



The above conception is not opposed to the theory that the 

 so-called sex chromosomes are associated with the phenomena 

 of sex in many cases. The evidence indicates, however, that 

 they are only one link in a series of processes which result in sex 

 determination, and that other factors may operate so a^ to 

 change development, in spite of the presence of the sex chromo- 

 some. The physiological action of the sex chromosome may be 

 fundamentally the same as that of other factors. 



Finally, if we think of sex as an hereditary character, as it 

 seems we must, then it is amply demonstrated that here we have 

 an hereditary character that can be modified by a variety of 

 circumstances. Unless we assign the sex character to another 

 category than other hereditary characters, we are forced to 

 acknowledge the possibility that other hereditary characters are 

 modifiable also. If this should prove true, it is possible that the 

 idea that the sex character is changeable will be accepted with 

 less reserve than heretofore. 



