10 THE PHYSIOLOGY OF INSECT SENSES 



connexions directly with the central nervous system. From time to 

 time peripheral ganglion cells have been described, but these not 

 infrequently turn out to be non-neural cells. On the other hand, one 

 of the more recent reports, that of Peters (1961) describing a multi- 

 polar neuron in the labellum of flies, warrants further investigation. 



While it has generally been accepted for some time that sense cells 

 arise by mitosis from epidermal cells (vom Rath, 1888, 1895, 1896; 



Fig. 3. A 'circular nerve' in the integument of fourth-stage larva of 

 Rhodnius and the cell bodies from which it was derived following an 

 extensive burn of the cuticle in the third-stage. (Redrawn from 

 Wigglesworth, 1953.) 



Haffer, 1921; Hanstrom, 1928; Snodgrass, 1935) (Fig. 2), proof that 

 the cells are primary sense cells is of relatively recent origin. Vogel 

 (1 923 b) claimed that in Hymenoptera the sensory axon grows out from 

 the central nervous system and joins the sense cell. Newton (1931), 

 Henke and Ronsch (1951), and Krumins (1952) maintained that the 

 epidermal sense cells differentiate axons which then grow centripetally 

 to join the central nervous system. The matter would seem to have 

 been settled, at least for Rhodnius prolixus, by Wigglesworth (1953), 



