GENERAL CHARACTERISTICS OF THE SENSORY SYSTEM 13 



accurate touch localization. On the other hand, fusion of axons within 

 groups of campaniform sensilla, hair plates, and some chordotonal 

 sensilla does occur in the leg of the cockroach (Pringle, 1938 a; 

 Nijenhuis and Dresden, 1952). 



A B 



Fig. 6. Diagrammatic representation of two types of ommatidia. A. Apposi- 

 tional type of diurnal Lepidoptera. B. Superpositional type of nocturn- 

 al Lepidoptera. Co, cornea; Cp, corneal process; Cn, crystalline cone; 

 CnN, crystalline cone nuclei; R, retinal cell; Rh, rhabdom; T, tracheal 

 tapetum. (Redrawn from Snodgrass, 1935 after Nowikoff.) 



The presence or absence of fusion is a matter of considerable 

 importance to the electrophysiologist, who must try to interpret 

 recordings from afferent nerves. Another unsettled question of 

 importance is whether or not the large cells frequently observed at 

 the junction of uniting nerves or axons are multipolar nerve cells. 

 If they are, it means that a synapse is interpolated between the 

 peripheral sensory neuron and the central nervous system. Otherwise, 



