438 HOMEK WHEELON 



the generative tract, and the characteristic male hirsutis. It arrests the 

 proper development of the chest and pelvis, preserves the high-pitched 

 voice of youth, and retards the closing of the epiphyses (Tandler and 

 Gross) . 



2. The Relation of Somatic Sex Characters to Secondary Sexual 

 Characteristics. The above discussion, in brief, shows the relationship 

 of the gonads to the somatic sex characteristics. The phrase "somatic sex 

 characteristics' 7 is used advisedly, for it is apparent that sex dimorphism 

 is not maintained in all forms of animals because of the type of repro- 



Fig. 3. Photograph of guinea pigs showing the effects of "masculinization"' on 

 somatic development. A, "masculinized" sister; B, castrated sister; C, normal sister; 

 D, normal brother. (Steinach and Holzknecht, 1916, Fig. 1, p. 492.) 



ductive tissue present. Somatic sex differentials in lower forms and, to a 

 certain degree, among the higher animals are absolutely independent of 

 gonadal influence of either sex. Such characters, therefore, should not be 

 classed as Secondary Sexual Characters, but rather as Hex Associated 

 Characters. On the other hand, those sex differences which depend upon 

 the presence of functioning gonads are properly classed as Secondary 

 Sexual Characteristics because, as the term implies, they are dependent 

 upon the primary sex organs for their development and maintenance. Sex 

 associated characters are as old as sex itself, but secondary sexual char- 

 acters appeared relatively late in the evolution of sex. Moreover, these 

 characteristics appeared gradually, and evolved along different lines in 

 the various types of animals. Therefore, we may justly conclude that in 

 many forms of life certain characteristics of sex are dependent upon the 

 presence of normal reproductive organs, and that certain cells respond to 



