GENERAL CHARACTERISTICS OF THE SENSORY SYSTEM 11 



who proved by interrupting sensory nerves that axons are regenerated 

 by epidermal cells and grow centripctally until they encounter a 

 nerve. If they do not encounter a nerve or if they become trapped 

 above the basement membrane, which separates the epidermis from 

 the rest of the body space, they grow in loops and circles, apparently 

 indefinitely (Fig. 3). 



Nc Oc 



Fig. 4. A. Stages in the moulting of sensilla in a fourth-stage larvae of 

 Rhodnius. B. Campaniform organ (haematoxylin). C. Tactile hair 

 (haematoxylin). D. Campaniform organ (Romanes' method). E. 

 Tactile hair (Romanes' method). N, nerve; S, sense cell; Dp, distal 

 process; A, axon; Tr, trichogen ; To, tormogen; Nc, new campaniform 

 organ; Oc, old campaniform organ; Ns, new seta; Os, old seta; Ni, 

 neurilemma cell; Nso, new socket; E, extension of distal process from 

 new to old seta. (Redrawn from Wigglesworth, 1953.) 



