422 LECTLRE xvin. 



" Were a naturalist to announce to the world the discovery of an 

 animal, which for the first five years of its life, existed in the form 

 of a serpent ; which then, penetrating into the earth, and weaving a 

 shroud of pure silk of the finest texture, contracted itself within 

 this covering into a body, without external mouth or limbs, and re- 

 sembling, more than anything else, an Egyptian mummy ; and which, 

 lastly, after remaining in this state without food and without motion 

 for three years longer, should, at the end of that period, burst its 

 silken cerements, struggle through its earthly covering, and start 

 into day a winged bird, — what think you would be the sensation 

 excited by this strange piece of intelligence ? After the first doubts 

 of its truth were dispelled, what astonishment would succeed ! 

 Amongst the learned, what surmises 1 what investigations ! Amongst 

 the vulgar, what eager curiosity and amazement ! All would be in- 

 terested in the history of such an unheard-of phenomenon ; even the 

 most torpid would flock to the sight of such a prodigy." * 



Now a marvel of this kind, in all its essential features, is mani- 

 fested in this country under a thousand modifications. You will 

 witness it, if you trace the life of the common beetle from the egg, or 

 watch the same course of changes in the silk-worm. 



The first form under which insects appear after quitting the ovum, 

 is called the larva, a name devised by Linnseus, to signify, that 

 beneath this worm-like or snake-like guise there was masked a 

 higher form. The second stage is the pupa or chrysalis ; and the 

 third and last stage is the imago, as being the image to which all the 

 former stages tended. 



Linnaeus gave, also, precise terms to the different conditions of the 

 pupa- state of the insect ; and these terms have been applied by some 

 entomologists to characterize metamorphoses generally. When the 

 last larval skin or sheath of the pupa shows no signs whatever of the 

 limbs or appendages of the creature within it, Linnaeus called it a 

 " coarctate pupa." When the pupa-case shows, as if by a kind of 

 sculpture in relief, the character of the organs beneath it, the pupa 

 is " obtected." When the pupa case forms a special sheath for all 

 the projecting parts and appendages, the pupa is " incomplete*" 



In all insects the development of the embryo proceeds, with a few 

 secondary and unimportant modifications, in the order which has just 

 been described. The subsequent changes of the insect consist in the 

 growth of all the parts, which takes place chiefly during the period 

 of the moult ; and in the gradual acquisition of the wings, which are 

 developed, either when tlie insect has reverted to the passive state 

 analogous to that of the ovum, as in the kinds of pupa above defined ; 



* CCLI. vol. i. Letter iii. p. 59. 



