No. 589] THE EUGSTEB GYNANDB OMOBPII BEES 43 



their chromosomes are resolved, and a spindle develops. 

 But these spindles lack centrioles at their poles. The mi- 

 totic figure that has reached this stage then proceeds to 

 degenerate. The absence of the centrioles indicates, 

 Boveri thinks, that the spermatozoa of the bee does not 

 bring in a division center, hence this cell organ must be 

 contributed by the egg, and in consequence we can now 

 easily understand how facultative parthenogenesis is, so 

 to speak, a normal phenomenon in this egg. Boveri does 

 not point out however that Nachtsheim's figures show that 

 the polar spindles of the bee's egg also lack centrioles, and 

 yet mitotic division is accomplished. It seems highly 

 questionable therefore whether much weight is to be at- 

 tached to the absence of centrioles in the supernumerary 

 sperm figures. The chief interest that attaches to Bo- 

 veri 's argument is his disclaimer that he intended his 

 striking statement in regard to fertilization, namely, that 

 the sperm furnishes the dynamic division center for de- 

 velopment, to be taken as a universal dictum. The incite- 

 ment of artificial division centers in such eggs as those of 

 the sea urchin in which the sperm brings in the centriole 

 (or causes its development in the immediate vicinity of the 

 sperm nucleus) shows how little importance can be at- 

 tached to the hypothesis of the genetic continuity of the 

 centrosome. If in the case of the bee three or more 

 sperm enter each egg all bees would be gynandromorphs 

 should all the sperm develop. Obviously, some special 

 condition must be assumed to be present if these sperms 

 are to go forward and complete their development which 

 they begin even under ordinary circumstances. Boveri 

 himself must also invoke some special condition, such as 

 retarded fertilization, in order that one of the entering 

 sperm fuses with one of the products of the first division 

 of the egg nucleus. It might equally well be postulated 

 that delay in the fertilization and the consequent impetus 

 to parthenogenesis might be favorable for the completion 

 of the division of the supernumerary asters. In a word 

 it is doubtful if Boveri's interpretation gains much from 

 his cytological argument. If his observations on the dis- 



