AND THE LOWER ANIMALS. 225 



This is clearly the doctrine of compound concentric 

 tjerms. In the Aphides there intervene between the two 

 sexual generations, ten or twelve agamic ones, and, as 

 we have also seen, an insect which is produced from a 

 single egg gives rise to thousands of millions of indi- 

 viduals. Steenstrup's theory would force us to admit 

 that the ovum contained this enormous number of 

 germs enclosed one within the other. Such a conclusion 

 is hardly more admissible than Bonnet's Panspermy. 



Steenstrup endeavoured to render his views clearer 

 by a comparison, or even by an assimilation, which, to 

 my mind, does not appear more exact than the views 

 themselves. He supposes that the nurses, or, in other 

 words, the scolices of the Aphis, Medusa, and Salpa, 

 represent the neuters in a colony of bees, wasps, 

 or white ants, only they are placed lower in the scale 

 of development. " A female wasp/' he says, cc having 

 survived the winter, and being isolated, at first con- 

 structs a few cells, and deposits therein her eggs, from 

 which workers exclusively are developed. As soon as 

 these are hatched, they set themselves to work, 

 widening the comb and increasing the number of 

 cells. The mother now deposits a new series of ova, 

 and from this second batch neuters are produced, and 

 are nursed by the workers which are already there. 

 This goes on till the workers are insufficient numbers. 

 Then, and then only, there spring from a few eggs, 

 both male and female insects, and these are attended to 

 by the neuters with the utmost care. These processes 

 are repeated, each batch of sexual insects being pre- 

 ceded by one of agamic individuals destined to take 

 charge of it, to watch the eggs, to collect the common 

 aliment, and to feed the larvae, &c. These neuters, 



