OF THE NERVES. 183 



back; the cord then again separates, to reunite in the 

 mesothoraxj where it again gives rise to four nerves. After 

 forming the fourth, fifth, and sixth cerebroids, separating 

 in the same way between each, the cord proceeds, single 

 and united, to the propodeon, and through the other seg- 

 ments to the telum, leaving a distinct mass or cerebroid 

 in each segment, which invariably gives out four nerves, 

 two of which ascend to the back and the other two descend, 

 some entering the prehensile legs with which most cater- 

 pillars are furnished. In the telum is situated the thirteenth 

 and last cerebroid or teli cerebroida, and this gives off no 

 less than eight nerves, most of them permeating the organs 

 of generation : thus the number of main nerves arising 

 from the whole of the cerebroids in this caterpillar, is 

 sixty- two. 



The twelfth and thirteenth cerebroids are attached and 

 sessile without any intervening cord ; the spaces between 

 the others vary very rapidly as the insect approaches per- 

 fection. In the first place, the second cerebroid enters the 

 head, and becomes united with the first ; then the fifth 

 and sixth approach and unite ; then the third and fourth ; 

 lastly, in the pupa, the seventh and eighth wholly disap- 

 pear, and eight only are to be found in the perfect butterfly. 

 The nerves, after leaving the cerebroids, divide and ramify 

 almost infinitely, being more particularly abundant in the 

 head and tarsi ; they do not appear to penetrate the ossified 

 skin, although they are found close beneath it. 



The nerves are the means by which the circumstances 

 of matter are conveyed to the mind, and also the means 

 by which the commands of mind are conveyed to matter : 

 in the former capacity they are the organs of the senses. 

 The senses of insects are, properly speaking, seven : love, 

 touch, taste, smell, hearing, sight, and the commanding 

 and governing sense, called volition, mind, thought, or in- 



