472 INTERNAL SECRETIONS 



This classification met with much approval as being of great 

 practical use. But it is not without certain disadvantages. 

 The terms "essential" and "accidental" may give rise to mis- 

 understanding Poll says, that the sex gland is an "essential" 

 sex character as being of "prominent importance" (von 

 " iiberragender Wichtigkeit"). But what importance is here 

 meant? Importance in relation to propagation, or to inherit- 

 ance, or to the formation of "accidental" sex characters? If 

 "essential" means most important for the formation of the 

 accidental sex characters Poll's classification is nothing more 

 nor less than a classification into primary and secondary sex 

 characters on a genetic basis. Further, " extragenitales " may 

 mean: (i) sex characters, which functionally have nothing to 

 to with the genital apparatus, and (2) sex characters which, 

 being localized far from the genetic apparatus, nevertheless are 

 functionally related to the latter, i.e., to the "genitales sub- 

 sidiariae," like the plumage, the larynx, the pads of the frog, 

 etc. 



For practical use I propose the following classification of sex 

 characters : — 



1. Endocrine sex apparatus. 



2. Generative cells. 



3. Somatic sex characters. 



{a) Characters of the copulatory and genital 



apparatus. 

 {b) Characters of the sexual auxiliary appaiatus. 

 (c) Characters of other organs. 



4. Functional sex characters. 



5. Neuro-psychical sex characters. 



The first two groups comprise the characters of the sex 

 glands. It is necessary, especially in the case of mammals, to 

 make two groups; even in attributing hormone-production to 

 the generative part of the sex gland we must admit that the 

 process depends not only upon the generative cells, but also 

 upon other parts of the organ. The group "sexual auxiliary 

 apparatus" includes all somatic characters, which, without 

 relating to the copulatory or internal genital apparatus, take 

 part in some manner in the performance of the sexual function ; 

 the plumage and larynx in birds, certain glands in various species 

 and the pads in the frog are examples. There are, however, 



