INSECTA. 367 



and, except the two last, at regular distances ; in the pupa the inter- 

 ganglionic columns are shorter, but the body, becoming still more 

 abbreviated and concentrated, throws those columns into curved 

 lines {^Jig. 146.). The eleventh and twelfth ganglions coalesce ; the 

 sixth and seventh disappear {ih. between the 5*^ and 8*^ ganglions in 

 the third subject) ; the fifth blends with the fourth, and the third with 

 the second ; thus leaving four ganglions in the abdomen and two in 

 the thorax (^Jig. 159). Corresponding changes take place in the 

 cerebral portion of the nervous system. The maxillary ganglion de- 

 creases with the diminution and change in the maxillary apparatus. 

 The oesophageal collar contracts, as does the canal which it surrounds. 

 The brain enlarges, having to supply organs of sense, especially those 

 of sight, which are perfected to correspond with the acquisition of 

 new and improved locomotive forces. (Compare the third with the 

 first subject va fig. 146). 



Analogous changes we may naturally conclude to take place in 

 other orders of insects ; and we find, indeed, in some of these that 

 the nervous system continues stationary at stages of development 

 which are progressive and transitory in the Lepidoptera, and that 

 further concentration is discovered to have taken place in the Melo- 

 lontha, Cicada, Ranatra, &c., than that which constitutes the highest 

 stage observed by Herold and Newport in the Lepidoptera. The 

 marvel is, that these changes, due in part apparently to mere me- 

 chanical influences, should be so regular, so orderly, so admirably 

 adapted in their final results to the general condition and exigencies 

 of the perfect insect : one might have supposed that the particles of 

 the soft and semi-fluid nervous matter, squeezed by the pressure of 

 the surrounding parts, when the body seems to be, as it were, con- 

 tracted by an universal spasm, would be irregularly dislocated or 

 aggregated into one or more masses ; but, on the contrary, we perceive 

 the nervous particles and ganglionic cells moving forwards and re- 

 arranging themselves in orderly groups, definite in their forms, in 

 their proportions, and in their relative positions ; these being appa- 

 rently regulated by a law of prospective arrangement and collocated 

 precisely in those situations where the greatest supply of nervous 

 energy is required to radiate from them in the active and perfect 

 insect. 



An idea of the situation and degree in which the sense of touch is 

 exercised in insects may be formed by observing the modifications of 

 the different parts of the integument, the papillae, or folds upon its 

 surface, the hairs, plumes, or soft jointed organs developed from par- 

 ticular parts of the body. The soft balls on the feet of grasshoppers, 

 the pulvilli and adhesive discs on those of flies, the extremity of the 



