ON 



THE PHENOMENA OF SEX-DIFFERENTIATION. 



S. WATASE. 



In the fifty-seventh Exercitation of his work On Anhnal 

 Gejieration, ^ Harvey states that he has frequently wondered 

 how it happens that the offspring, mixed as it is in so many par- 

 ticulars of its structure and constitution, and with the stamp of 

 both parents so obviously upon it in many parts, should still 

 escape all mixture in the matter of sex, and that it should 

 uniformly prove either male or female. 



An obvious inference that suggests itself from this point of 

 looking at the problem, as stated by Harvey, is that we may 

 here be dealing with two questions which are independent of 

 each other, viz. : 



(a) The phenomena of heredity, or the mixture of the parental 

 characteristics in the offspring ; (b) TJie phenomena of sexual 

 differentiation in the organism, in which the parental characters 

 have already been mixed. 



Without therefore weakening even in the least degree the sin- 

 gularly suggestive form in which Harvey's reflection is put, we 

 may for the sake of convenience separate the first half of the 

 paradox from the second and consider them separately as two 

 independent problems. We are, however, concerned at present 

 with the second portion of the problem only, or the phenomena 

 of sexual differentiation of the young developing organism in 

 which the materials representing two parental characters already 

 exist. It does not make any difference from our point of 

 view whether this mixture of parental characters has taken 

 place directly, in which case the embryo is the immediate out- 

 come of the sexually fertilized ovum, or indirectly, in which case 

 such mixture may have taken place some generations back, as 



1 On Animal Generation, 1651, London. The works of William Harvey, Willis' 

 edition, 1847, p. 429. 



481 



