52 P. W. WHITING. 



animals. It may result in the production of either males or 

 females, but in Hymenoptera it results in females only, the males 

 being haploid, with the possible exception of the saw flies (Don- 

 caster, 1907). Goldschmidt (1917) has given a convenient classi- 

 fication of types of parthenogenesis. 



From the work already done on Hadrobracon it appears that 

 parthenogenesis is strictly haploid and therefore arrenotokous. 

 The females are certainly diploid and arise in all cases from 

 fertilized eggs. But it does not therefore follow that all males 

 come from unfertilized eggs, or that such males as arise from 

 fertilized eggs are diploid. 



The suggestion has been made that males in Hymenoptera 

 might occur, having the number of chromosomes diploid, except 

 for the sex-chromosome, which might occasionally pass out in 

 the abortive division of the first spermatocyte. Fertilization 

 by the resulting spermatozoon would result in diploid males. 

 In Hadrobracon all males, thus far studied, even the anomalous 

 males, appear to be haploid for the orange locus. 



(c) The Bearing of Mosaics on Problems of Fertilization. -An 

 interesting problem in the occurrence of anomalous, mosaic 

 males centers in fertilization. In the physiological sense, fertili- 

 zation means the stimulation necessary to initiate development. 

 In forms which are normally parthenogenetic, this stimulation is 

 unnecessary and the entrance of the spermatozoon into the egg 

 can hardly be called physiological fertilization. The egg is 

 already fertile before the appearance of the male cell. In the 

 genetic sense, however, fertilization denotes the union of paternal 

 with maternal germ plasm, or amphimixis. In this sense an 

 egg producing an anomalous male is fertilized, for paternal germ 

 plasm is brought into it, although this is not followed by fusion 

 of nuclei, as is usually the case. 



In order to explain sex-mosaics or gynandromorphs it has 

 been suggested that a paternal nucleus might fuse with a mater- 

 nal, the diploid product giving rise to the female parts of the 

 embryo. Male parts are assumed to be derived from haploid 

 nuclei of paternal, maternal or mixed origin. Polyspermy has 

 been suggested by Morgan (1905) to explain the Eugster gynan- 



