REPKODTJCTION OF APHIDES. 109 



standing the wonderful dilution of energy which must 

 occur throughout the countless components of the 

 generations following.* 



The propositions made by the Swedish naturalist, 

 De Greer, in 1773, have been already noted. f He 

 agreed with Bonnet in the modifying action of food 

 and climate, and thought it highly probable that, if 

 Aphides should be discovered in tropical countries, 

 they would be exclusively viviparous. Leydig also 

 entertained very similar views on this point. 



KyberJ: made experiments on the effects of food 

 and temperature, and he came to the conclusion, which 

 is now untenable, that such influence was sufficient to 

 change the apterous oviparous female into the vivi- 

 parous female ; and this error seems to have been 

 shared by the French anatomist, Charles Morren. 



The close similitude of form of the ovarian chambers 

 of the true female and the chambers which develop 

 the germs from the viviparous individual doubtless 

 misled both these observers. The latter observer 

 made good dissections of the reproductive organs of 

 both male and female Aphides ; but he failed to note 

 the significant absence of a spermatheca in the vivi- 

 parous female. Such a knowledge also would have 

 saved Bonnet from the error of supposing that vivi- 

 parous germs and mature ova were often present in the 

 same insect. 



Considering the comparatively early date of Morren' s 

 memoir on the anatomy of Puceron du pecher, his 

 remarks and discussions are very suggestive. He 

 says it is very difficult to bring one's mind to accept 

 the hypothesis, that Aphides, up to the eleventh 

 generation, are the results of the fecundation of their 

 ancestors anterior to the first of the series. " The 

 eleventh generation," he says, " does not exist at the 

 moment of fecundation of the first." " He would 



* Prof. Owen's lecture, ' Proc. Roy. Instit./ vol. i, p. 9. 



f Vol. i, p. 55. 



X Kyber, ' Germar's Mag. der Entomol.,' 1815. 



