ON PARTHENOGENESIS IN THE HYMENOPTERA. 199 



Now, it is found that if both globules be thrown 

 out no development can take place unless the egg 

 be fertilised, the male sperm taking the place of 

 the germ-plasma removed when the second globule 

 was ejected, so that in this case the egg contains 

 the same amount of germ-plasma as the egg from 

 which only one globule has been thrown out, with 

 the distinction that one-half has been contributed 

 by the male sperm. Weismann discovered that eggs 

 from which only one globule had been removed 

 were parthenogenetic — in other words, the distinction 

 between sexual and parthenogenetic eggs is that the 

 former throw out two polar globules and the latter 

 only one. 



But while Weismann's observations are of funda- 

 mental importance in throwing light on sex, they 

 do not enable us to comprehend the origin and 

 meaning of parthenogenesis. In the case of the 

 honey-bee, it may be explained by the necessity of 

 economising the spermatozoa. Considering that a 

 queen will lay a million-and-a-half eggs during her 

 life, and that probably not much over four or five 

 million spermatozoa are ejected into her spermatic- 

 sac, the obvious benefit to the hive, if males can be 

 produced without spermatozoa, becomes apparent. 

 In the case of the aphides, I am inclined to believe 

 that natural selection may have been a factor in 

 producing parthenogenesis. A little consideration 

 will show that the aphides maintain their existence 

 entirely by their excessive fecundity ; they are merely 

 reproductive machines, their other faculties being to 

 a more or less extent subordinated to reproduction. 

 Certain wasps lay only 50 or 60 eggs ; but by a highly- 

 developed nervous system, by their nest-building 

 instincts, by skill, boldness, and courage in finding 

 food for their young, the species is preserved as 

 effectively as the aphis with its unlimited powers 

 of producing millions of young. I have just stated 

 that there are four degrees of parthenogenesis in 

 insects. In a work published six years ago,* I 



*Mon. Brit. Phyt. Hymen., i., pp. 25-30. 



