78 INTERNAL ORGANS. 



system, the seat of volition and sensation. In 

 discussing the earlier stages of the insect, we shall 

 next take up the glandular or secretory system, 

 since its sole independent representative is the 

 organ which serves to secrete silk, by means of 

 which the caterpillar is able to walk where it 

 needs to procure nourishment. These are all the 

 systems which have to do simply with the life of 

 the individual, but there is still another, the re- 

 productive, which must take the highest place as 

 related to the life of the species ; in tfye caterpil- 

 lar this remains in an embryonic condition, a con- 

 dition of preparation for future development ; 

 and finally we shall consider briefly the cellular 

 system, which is almost entirely confined to the 

 larval stage and is intimately related to all the 

 other systems. 



The celebrated Lyonet counted more than four 

 thousand distinct muscles in a single caterpillar, 

 but we will admire his wonderful patience only 

 at a distance, and merely remark that the mus- 

 cular system of caterpillars consists almost en- 

 tirely of flat ribbons, made up of simple muscular 

 fibre. The head, however, with its numerous 

 movable organs, forms a partial exception, for it 

 is mostly filled with conical muscular bundles, 

 lying in a compact mass side by side, with their 

 smaller ends attached to the mandibles by means 

 of a tendinous cord in which they all terminate, 



