Royal Physical Society. 35 



appreciate the true nature and relations of the nominally 

 various and distinct metamorphoses of insects, by watching 

 and pondering over the development of a cockroach (also an 

 orthopterous insect), which quits the egg as a crustacean. I 

 saw that it passed through stages answering to those at which 

 other insects were arrested : there was a period when its 

 jointed legs were simple, short, unarticulated buds, — when its 

 thirteen segments were distinct and equal, — when it was apo- 

 dal, — when it was acephalous."* This statement, I think, not 

 only entitles, but obliges us to hold, that it has been deter- 

 mined by observation that the larva of orthopterous insects 

 has been detected in the shape of a maggot passing the early 

 portion of its life in the egg.f 



Having arrived thus far, I was surprised to find Professor 

 Owen stopping here. I thought the necessary consequence of as- 

 suming that the early stage of the orthopteran was a caterpillar 

 in the egg, was, that it also passed the chrysalid state in the 

 egg. I could quite understand the perfect jointed insect being 

 eliminated at once out of the embryonic elements in the egg, 

 in the same way that a chicken is hatched ; but if the maggot 

 is once hatched instead of the chicken, I know of no means, 

 or no analogy, by which its vermiform character can be 



* Lectures on Invertebrate Animals, Ed. 1855, p. 437. 



t I am inclined to think that all insects pass a more or less considerable 

 portion of their larval state in the egg. Except on this assumption, I am at a 

 loss to account for the well-known fact of the exclusion of ichneumon flies from 

 the eggs of various insects, for I find difficulty in accepting the proposition that 

 these parasitic larvae feed on the yolk of the egg. The whole economy of the ich- 

 neumon seems to me opposed to this. All those which we can watch require 

 a living animated organism on which to feed ; and although the yolk might, 

 for a short period, retain its vital powers even after it has begun to be preyed 

 upon by the ichneumon, I apprehend such a period could only be brief. The 

 yolk would soon have its vitality destroyed by the intrusion of the parasite, 

 which would perish along with the decaying mass which its presence had cor- 

 rupted. It seems more consistent with their habits and economy, to suppose 

 that those minute parasites feed upon the larva already formed in the egg, or, 

 at the utmost, that they commence their ravages after the development of the 

 yolk into the larva has commenced, and reach their chrysalid state as the yolk 

 by its dying effort completes the larva, in the same way as the larger ichneu- 

 mons devour the excluded larvae, mining away their powers till they leave 

 them only strength to pass into the chrysalid state simultaneously with them- 

 selves. 



