INFLUENCE OF AGE OF MOTHER. 



TABLE D. 



381 



MALES OF STRAIN DEFICIENT IN GENITALIA AND ANTENNAE ARRANGED ACCORDING 



TO AGE OF MOTHER (VIALS). 



It may be concluded that age of mother is an effective factor in 

 determining this type of deficiency. 



DISCUSSION AND SUMMARY. 



Deficiency or reduction in antennae, in external genitalia, and 

 in posterior part of the digestive tract occurs occasionally in 

 individuals of normal stocks. 



Two cases of marked hereditary deficiency present some 

 interesting points of difference. In one, deficiency in genitalia 

 was associated with deficiency in digestive tract and many 

 immature deaths occurred. The trait was increased and main- 

 tained by selection but very few fraternities approximated 50 

 per cent, even among the males. Great variability in ratios in 

 the different fraternities and failure to recover the stock by 

 breeding normal up to males of selected deficient indicate that the 

 character is genetically complex. 



In the other case, deficiency in genitalia was associated with 

 deficient antennae. There was no increase in immature deaths 

 over those normally occurring but much female sterility. The 

 line originated from a female from stock supposedly normal. 

 Fraternities fell into at least two groups. In one the deficient 

 averaged 2.6 per cent, of the total and were deficient either in 

 genitalia or in antennae but not in both. In the other they 

 averaged 45.8 per cent, of the total, the majority of them being 

 deficient both in antennae and in genitalia. The facts indicate 

 genetic complexity. 



Percentage of deficient offspring varies according to age of the 

 mother in both cases. It increases up to approximately the tenth 



