xiv TRANSLATOR'S PREFACE. 



in his work, is peculikrly interesting, on account of its occurring 

 in a family where such phenomena were regarded as highly 

 exceptional. This case was first pointed out by Bonnet, and was 

 the production of young aphides for several successive generations 

 without any union of the sexes. The virgin- aphides, however, 

 thus producing viviparous young, were not true females. These 

 eventually appear, producing eggs, from which proceed the 

 virgin generation. These virgin- aphides are truly " nurses/' 

 according to Steenstrup's theory. But a further development of 

 this strange history remains. Not only have we the lower 

 animals in their various stages of development, capable of pro- 

 ducing buds, or individuals like themselves, without sexual union, 

 and embryo-bearing eggs, but we have also amongst the Articulata, 

 both in Crustacea and Insects, females producing eggs, which 

 proceed to the development of perfect animals without any sexual 

 intercourse or union of sperm-cells and germ-cells. 1 Such a 

 phenomenon is so opposed to the universally accepted dogma of 

 the necessity of sexual intercourse for the development of the 

 embryo, amongst the higher animals, that many physiologists of the 

 present day have not hesitated to express their unqualified dissent. 

 Regarding, however, the phenomena of reproduction from the 

 point of view afforded us by the Entozoa, and other forms of 

 lower animals, we must receive the facts in both cases equally 

 cautiously, and judge according to the evidence. Von Siebold, 

 in his work on f True Parthenogenesis/ affords good evidence 

 for believing that the queen-bee deposits two kinds of eggs, 

 the one of which has come under the influence of the sperm- cells 

 of the male, and the other not. A very curious point in this 

 history, is the fact that, whilst both eggs produce young bees, 

 the impregnated eggs produce worker or female bees, whilst the 

 unimpregnated eggs produce male or drone bees. In a recent 



1 ' On a true Parthogenesis in Moths and Bees ; a contribution to the History of 

 Reproduction in Animals,' by Carl Theodor Ernest von Siebold, translated from the 

 German by William S. Dallas, F.L.S., London, 1857. 



