194 CARL G. HARTMAN AND WILLIAM F. HAMILTON 



the experimental side, the work on mammals is in a much more 

 satisfactory state. For example, experiments have hardly been 

 begun on the masculination of pullets and hens and on the 

 production of avian hermaphrodites by transplantation of the 

 gonads. 



It would be interesting, moreover, to note the result of cas- 

 tration of a spontaneously occurring hermaphrodite such as 

 the one here described — a manifestly difficult operation. Such 

 an animal should also be studied cytologically in order to deter- 

 mine whether the ZY or the ZZ condition prevails in the soma of 

 the specimen.^ Cytological studies of gynandromorphs among 

 the vertebrates would also go far toward differentiating genetic 

 from physiological factors in the problem. Indeed, it is of 

 prime importance for the experimenter to know the genetic 

 substratum of the material upon which he works (cf. Morgan, 

 '19). For example, in some races of fowl the females have large 

 combs, in others small ones; in some strains a large proportion of 

 the females are normally spurred, in others a spurred female 

 occurs never or very rarely. Again the sexual activity of the 

 fowl may influence certain secondary sex characters, for example, 

 the size of the comb, which may increase as much as 130 per cent 

 in area before the egg-laying period (Smith, '11a). Lack of 

 information like this can only lead to confusion. 



In conclusion, we bring before the reader table 2, pages 196 

 and 197, in which the secondary sex characters are classified 

 according to the physiological or genetic causes underlying them. 

 The classification is to be considered strictly tentative, and is 

 presented as a possibly useful basis for further discussion. 



* We attempted this investigation, but, due to the well-known difficulties with 

 the fixation of chicken material, we were unable to arrive at a satisfactory con- 

 clusion. Counts of eight haploid plates gave either seven or eight chromosomes. 

 The spermatogonial plates were not very clear and we were unable to be sure of 

 any sex elements. 



