GENERAL CHARACTERISTICS OF THE SENSORY SYSTEM 21 



They were called chordotonal organs by Graber (1882 a) because 

 many of them stretched like taut cords from point to point and were 

 believed to be auditory organs. Those with a terminal strand were 

 termed amphinematic because they appeared to be stretched between 

 two threads; the others were termed mononematic (Graber, 1882 a). 

 It soon became clear that these sensilla were neither exclusively audi- 



FiG. 14. A thick-walled sensillum basiconicum from the antenna of a 

 grasshopper. N, bipolar neuron; S, scolopoid sheath; A, axons; 

 D, dendrites; Tr, trichogen cell; To, tormogen cell. (Redrawn from 

 Slifer et al., 1957.) 



tory nor always cord-like in appearance. In recognition of the 

 universal existence of a peg-like rod within them, Eggers (1923, 1924, 

 1928) proposed that they be called scolopophorous or scolopal organs. 

 With this terminology one sensillum would be called a scolopidium 

 (by analogy with the ommatidium of the eye) and a group of scolopidia 

 comprising a unit would be termed a scoloparium. Even Eggers 

 admitted, however, that other kinds of sensilla possessed peg-like 



