24 NATURAL HISTORY. [CH, I. 



skin which covers them, even without the assist- 

 ance of the microscope. The extremities of the 

 legs are now observed to move very distinctly, and 

 the wings begin to enlarge, so that it is no longer 

 possible for the brittle skin which covers the whole 

 to withstand the struggles of the enclosed butterfly ; 

 it accordingly gives way by a longitudinal slit down 

 the middle of the back, behind the head, where 

 there is usually a suture for the purpose. The slit 

 rapidly extends along the head down the breast on 

 each side of the cases of the antennas, so that the 

 skin of the chrysalis is burst into four distinct and 

 regular pieces, one of which enclosed the antennae, 

 legs, and tongue, another the abdomen, and the 

 other two the two pairs of wings. From this slit 

 the butterfly now emerges ; but the insect has not 



only to disengage itself from the hard outer skin : 

 we have also seen that the different limbs are 

 separately enclosed in sheaths, which become sol- 

 dered together by an external glutinous secretion 

 (forming when dried the outer skin) ; as, however, 

 the skin which covers these various parts on the 

 inside is extremely delicate and tender, from not 

 being exposed to the air, it all breaks and flies off 

 without any certain order ; hence it arises that so 

 many broken and ragged membranes, almost as 



