98 SEX INHERITANCE 
genetic female producing many sons, according to 
whether she has been fertilized soon after hatching 
or not. The nature of the change in this female is 
not known, but it is known that the small male- 
producing eggs extrude two polar bodies, thus be- 
Fig. 33. — Hydatina senta. — A, the ordinary parthenogenetic female. 
B, sexual female, at time of hatching, when she is fertilized by the male. 
C, male. D, parthenogenetic female egg. #, parthenogenetic male egg. 
F, fertilized resting egg. (After Whitney.) 
coming haploid. These males produce two kinds of 
sperm, functional and non-functional; there are 
just twice as many of the former as of the latter 
(Whitney). In this respect the case appears similar 
to that of the hornet, the male of which is haploid 
