No. 591] TRANSMISSION OF DEGENERACY 



109 



with a higher fertilizing power than the male-producing. 

 Such individuals will more frequently beget female off- 

 spring. Slight differences in the physiological behavior 

 of the two classes of spermatozoa would account for the 

 sex ratios in all animals, and finally, as Morgan has 

 shown, the extreme difference between the qualities of the 

 two classes of spermatozoa leads to the degeneration of 

 one entire class and the necessary production of only one 

 sex from the fertilized eggs of these species. Such spe- 

 cies must also be parthenogenetic in order to produce in- 

 dividuals of the other sex. 



This discovery by Morgan suggests, as Wilson ('11) 

 brings out in his review of the sex chromosome question, 

 a plausible explanation of the sex ratios in different 

 classes of animals. And we believe the evidence pre- 

 sented above lends further support to such an interpre- 

 tation. 



A rather old popular idea in attempting to explain the 

 sex riddle may have some ground of fact from the stand- 

 point of the variations in the differences of fertilizing 

 power of the two classes of spermatozoa. It has often 

 been claimed that one testis is male-producing and the 

 other female-producing. Every one knows that this is 

 untrue. Yet one testis may have a tendency to produce 

 spermatozoa of the female class with a higher fertilizing 

 power than the male sperm of this testis, and the other 

 testis might have an opposite tendency, since the condi- 

 tions of behavior often differ in two organs of a bilateral 

 pair. An animal which has produced a large proportion 

 of male offspring may after semi-castration produce al- 

 most all female offspring. A possible explanation for 

 such an occurrence would be that the removed testis had 

 produced more vigorous male sperm than female and the 

 spermatozoa of this testis possessed the higher fertilizing 

 power, while the remaining testis tended to produce more 

 potent female sperm. On removing the one testis the 

 other came into supremacy. In the same imaginary case, 

 if the opposite testis had been removed, there would have 



