IL] METAMORPHOSES OF INSECTS. 39 



development of the egg into the imago ; and this 

 might more especially appear to be the case with 

 those insects in which the larvifi offer a general re- 

 semblance in form and structure (excepting of course 

 so far as relates to the wings) to the perfect insect. 

 Nevertheless we see that this would be a very incom- 

 plete view of the case. The larva and pupa undergo 

 changes which have no relation to the form which 

 the insect will ultimately assume. With a general 

 tendency to this goal, as regards size and the de- 

 velopment of the wings, there are coincident other 

 changes having reference only to existing wants 

 and condition. Nor is there in this, I think, 

 anything which need surprise us. External circum- 

 stances act on the insect in its preparatory states, 

 as well as in its perfect condition. Those who 

 believe that animals are susceptible of great, though 

 gradual, change through the influence of external 

 conditions, whether acting, as Mr. Darwin has sug- 

 gested, through natural selection, or in any other 

 manner, will see no reason why these changes should 

 be confined to the mature animal. And it is evi- 

 dent that creatures which, like the majority of insects, 

 live during the successive periods of their existence 

 in very different circumstances, may undergo con- 

 siderable changes in their larval organization, in 

 consequence of forces acting on them while in that 

 condition ; not, indeed, without affecting, but certainly 

 without affecting to any corresponding extent, their 

 ultimate form. 



I conclude, therefore, that the form of the larva 

 in insects, whenever it departs from the hexapod 



