312 THE MECHANICAL FUNCTIONS. 



fully arranged with reference to the motions 

 they are intended to effect. The investigation 

 of the structure of these minute organs has long 

 exercised the talents of the most skilful entomo- 

 logists, and still offers much that remains to be 

 explored. The researches of Lyonet, already 

 alluded to, on the anatomy of the larva of the 

 Bombyx Cossns* of which he has published an 

 elaborate description, accompanied by admi- 

 rable engravings, will ever remain a splendid 

 monument of patience and ingenuity in over- 

 coming the difficulties which impede this kind 

 of inquiry. In the body and the limbs of this 

 caterpillar, Lyonet counted above 4000 sepa- 

 rate muscular bands, all arranged with the most 

 perfect symmetry, and adapted with wonderful 

 precision to the performance of the required 

 effects. 



In these larvae, as in the simpler forms of 

 the Annelida, progression is often accomplished 

 solely by the alternate contraction and exten- 

 sion of the annular segments, aided, in many 

 cases, by short hairs, and frequently, also, by 

 a slimy secretion which exudes from their bo- 

 dies. Many larvae which are destitute of feet, 

 move onwards by first coiling the body into a 

 circle, making the head and the tail meet, and 

 then springing forwards by a sudden extension 

 of the back, producing an effect like the un- 



* Cossus liyniperda. Fabric! us. 



