l86 THE EVOLUTION OF SEX. 



supposition, both in general and in this particular case. Again we must 

 note, that if parthenogenesis be decided on utilitarian principles, and if the 

 difference of sex need not be taken into account, and if the eggs are all the 

 same to start with, we see some difficulty in understanding the persistence 

 of drones and sexual reproduction at all. It is a laborious and expensive 

 way of attaining no obvious gain. But we should, indeed, like to be sure 

 that the ova are all the same to start wiih. Von Siebold said that the 

 queen was moved by the sight of the different size of the cells to fertilise 

 or refrain from fertilising. This may be so. Impressive as a queen's cell 

 is, the difference between a worker's and drone's is much less striking. We 

 suspect the impulse lies somewhere else. But barring this, the eggs laid 

 first, when the queen is at its prime, develop into females ; the eggs which 

 give rise to drones come later, when the mother is more exhausted. They 

 have had less chance of differentiation — they are parthenogenetic ova. So 

 with old queens, when the stock of sperms is also of course exhausted. 

 Weismann quotes the experiment which Bessels made, after Dzierzon. The 

 nuptial flight was prevented, and ova which, in the course of nature, would 

 have been fertilised and given rise to queens and workers, were of course 

 unfertilised, and developed parthenogenetically into males. This proves, 

 he says, that the ova are all the same to start with. But one would like 

 to know whether the prevention of the nuptial flight had not also its effect 

 upon the ova, and whether the parthenogenetic ova are not always less 

 differentiated. 



