NO. 2242. MORPHOLOGY OF THE STREPSIPTERA— PIERCE. 401 



Now, it is quite clear that the mitotic spindle must represent the first polar 

 body in pi'ocess of division. There is, however, no trace of a second polar body, 

 which there certainly ought to be if a second polar body was given off and fertili- 

 zation effected in the usual way. 



Since Brues differs with Smith and Hamm concerning the numbers 

 of polar bodies we may safely claim that in neither case has partheno- 

 genesis been proved. 



The fifth reason is that — 



Actual copulation by the male has never been adequately observed. 



Since Smith and Hamm claim to have consulted Bulletin 66, al- 

 though they incorrectly refer to it, they evidently are indisposed to 

 accept the three definite records of copulation having been observed, 

 as recorded therein. It is difficult to conceive how one can more ade- 

 quately observe the act of copulation. 



As a supplemental reason they state that — 



In a large number of colonies of Infected Andrena it would appear that the 

 male parasite is very much scarcer than the female, and in certain cases may 

 have almost entirely died out. 



It is of interest therefore to note the many records which have 

 been tabulated by the writer on the sex of parasites. Up to the 

 present time the tabulation of all counts of sex by various observers 

 gives 1,318 males to 634 females. Of course no account has been 

 made of the many miscellaneous single observations of stylopisation 

 listed m the host lists of the order. 



The evidence for parthenogenesis therefore consists of an in- 

 ability to explain how the spermatozoa, which are conceded to exist', 

 can reach the eggs, and of contradictory interpretations of the polar 

 body and maturation phenomena observed in a limited number of 

 cases. The burden of the proof lies with the advocates of partheno- 

 genesis. 



It is of course possible that parthenogenesis may occur in some 

 cases, but its existence is still a matter of doubt. 



Oogenesis. 



Hoffman (1913) presents a very complete embryological study of 

 a parasite from an undetermined host from Paraguay beginning with 

 the blastoderm and carrying it to the triungulinid. This parasite 

 was later (Hoffman, 1914b) described as Xenos hohlsi. He finds 

 eggs in all states of development in the same parent and not all 

 developing uniformly as found by Brues (1903). He shows the 

 nervous system in the early embryos to consist of a cerebral ganglion 

 and a ventral ganglion reaching to the eighth abdominal segment, 

 but this gradually shortens until it lies in the third or fourth ab- 

 3343— 19— Proc.N.M.vol..^4 27 



