The determination of sex in animal development. 729 



by VON SiEBOLD 1), who from a long series of experiments thought he 

 had proved, that as in the bee non-fertilisation of the eggs induced 

 the development to the male sex. In four of his experiments with 

 the sexes of the eggs produced by virgin-females he unexpectedly 

 obtained a few females among the male young produced in each case. 

 The results are as follows: 



No. of experiment male cocoons female cocoons 



13 265 2 



14 493 2 



15 374 8 



16 168 1 



That is to say, in not fewer than four out of nine ex- 

 periments one or more females appeared among the parthenogenetic 

 young. VON Siebold accounts for this by supposing, that in these 

 cases young laid in nature by fertilised females had by accident been 

 introduced with the food into his cultivations. 



The acceptation of this explanation would vitiate the experiments, 

 for it would be clear, that proper precautions had not been taken. 

 Quite apart from the unnecessary multiplication of causes — "entia 

 non sunt multiplicanda praeter necessitatem" 2) — the zoologist, who 

 has read, and admired, von Siebold's record of patient observations, 

 and who can realise the significance of the new facts and factors of 

 the present writing, will probably attach far greater weight to the 

 care and precautions of the observer, than to any such needless hypo- 

 thesis. 



The case of the bee is the only one, in which a supposed in- 

 fluence of fertihsation upon sex, has ever appeared at all plausible. 

 In face of the actual facts concerning it, of the glaring contradictions af- 

 forded by the observations of Dzierzon, Perez, Mulct, Dickel, Bessels, 

 and others, of the conditions in other insects such as the gall-flies, 

 of von Siebold's observations upon Nematus ventricosus, of the known 

 existence of sexually differentiated eggs in certain examples from the 

 Rotifera, Insecta, and Vertebrata, of the existence, so far as we know 

 and can judge, of but one form of functional gamete in the male, it 

 is not logical or reasonable to generalize from it, that fertilisation 

 influences the sex of the offspring, or that this holds even for the bee. 



1) VON Siebold, C. T. E., Beiträge zur Parthenogenesis der Arthro- 

 poden, 1871, p. 106—130. 



1) William of Occam's Razor. Vide Kakl Pearson's Grammar of 

 Science, 2. edit., London 1900, p. 537. 



