GENERAL CHARACTERISTICS OF THE SENSORY SYSTEM 15 



cuticular processes but lying instead on the inner face of the body wall, 

 the walls of the alimentary canal, muscles, and connective tissue 

 (Type II). Only the cells of photoreceptors lack an obvious distal 

 process or dendrite, although even in these cells the distal end is 



B • ^ 



Fig. 8. Type II neurons. A. The hypopharynx of termites. (Redrawn from 

 Richard, 1951.) B. The muscles of the mid-gut of Melolontha larvae. 

 C and D. The muscles of the oesophagus of Oryctes larvae. (Redrawn 

 fromOrlov, 1924.) 



structurally modified (Fig. 6). Depending on the position of the 

 neurocyte with respect to the epidermis. Type I neurons are termed 

 intraepidermal or sub-epidermal, but there are certainly all gradations 

 between the two positions. 



The ontogenetic origin of Type II neurons from the ectoderm has 

 not yet been determined (Snodgrass, 1935). Numerically they are less 



