576 



HEEBEET M. EVANS 



stages has fijmly established this general conclusion. Furthermore, the 

 varying effects of castration have become intelligible to us on the assump- 

 tion of the existence of an asexual embryonal form (Tandler, Gross, 

 Keller). This latter hypothesis, while possessing opponents, seems best 

 fitted to coordinate all of the facts. According to it the germ cells of the 

 new individual, the sex of which has been determined by chromosome con- 

 stitution, begin to affect the somatic cells at a very early and certainly 

 embryonic period, 4 though the soma possesses certain inherent tendencies 

 to express itself in a neutral, or asexual, form. Could castration be carried 

 out sufficiently early, such a neutral form would always result, a single 

 sex-undiffereiitiated form which would bo characteristic of the species. 

 Either the male or female may exhibit traces of this embryonal form, and 

 the testis or ovary may either act to suppress the neutral embryonal form 

 or to create a new form peculiar to the particular sex. Only actual experi- 

 ment will discover whether in any given species a supposed sex character 

 is actually such or is the survival of the common or neutral form. A 

 survey of such a viewpoint is furnished by the appended table. 



GENETIC SYSTEM OF THE SEX CHARACTERS 

 (ACCORDING TO LIPSCHUTZ) 



Instances 



Mammals 



Birds 



Plumage of the cock. 

 Spurs of the cock. 



So-called sex characters not dependent Body temperature of 

 for their development upon the sex the male, 



glands and representing the retention Mammary gland of Head furnishings of 

 and development of characters of the the male. the hen. 



asexual embryonal form. 



2. Sex characters dependent for their de- 

 velopment upon the sex glands. 



(a) Arising through synergistic 

 action of the sex gland. 



(b) Arising through antagonistic 

 action of the sex glands. 



Penis, 



Prostate 



Seminal vesicles and 

 increased body 

 growth of the 

 male. 



Uterus, mammillae, 

 mammce and in- 

 creased body 

 temperature of the 

 female. 



Reduction of the 

 Miillerian duct in 

 the male. Reduc- 

 tion of the Wolf- 

 , fian duct, clitoris 

 and slighter body 

 growth of the fe- 

 male. 



Comb and wattles of 



the cock. 

 Syrinx of the cock. 



Plumage of the hen. 

 Absence of spurs in. 

 the hen. 



4 See for instance the very important work on the free martin by Lillie (6) (c) 

 and by Keller and Tandler. 



