514 Mr. C. R. Narayona Rao on the Anatomy of 



obviously the fibres springing from tlie other kind of cells 

 with a single nucleolus must be motor in function. The 

 margins of the cord and ganglia are composed of small oval 

 cells Avith no fibres. The nucleus of tiiese cells is small 

 and stains deeply. 



In the oesophageal ganglia the giant cells form almost an 

 outer layer of cortex, while the oval cells aggregate round 

 the bases of the nerves. The neurons are more deeply 

 situated, but always in groups of four and four. The paired 

 cells are absent from the two ganglia, and perhaps have been 

 modified into neuroglia tissue or, better, neuroglia cells. 

 Each of the neuroglia cells found associated with the groups 

 of sensory and motor neurons is conical in outline, with 

 nervous fine fibrils spread out among the other cells which 

 they bind. Their bi- and trinuclear condition shows the 

 syncytial tendency of these paired cells. 



The communicatory dendrites of the sensory and motor 

 neurons form an intricate plexus round the giant cells, which, 

 perhaps in addition to the trophic function, may act also 

 as a centre of cognition, and, though the absence of any 

 processes from these large cells is not in favour of this view, 

 yet their serial repetition in the cord, their position, and 

 relation with the neurons on the oesophageal ganglia 

 strongly point to their cerebral function. 



The tactile bodies are the sensory epidermal swellings 

 round the setae, which just project beyond the surface of these 

 whitish cutaneous swellings (PI. XVII. fig. 7). In sections 

 of skin taken in this region the swellings are noticed to 

 occupy the distal half of the setal follicle, and are composed of 

 two kinds of sensory elements. Those which are more filiform 

 are apparently associated with the perception of movements, 

 and hence are not sensory in the true sense of the term. They 

 are closely related with the muscle-fibres which move the 

 setse and have also nerve-endings. The other kind of cells 

 with which the filiform variety enters into intimate relation 

 are shorter, spindle-shaped, with a granular deeply staining 

 cytoplasm and central nucleus and nucleolus. These cells, at 

 whose proximal ends the sensory fibrils enter, are more 

 or less enclosed in a connective tissue vesicle, and hence 

 constitute a true tactile organ. Between these cells enclosed 

 in the vesicle is a small quantity of granular matter, which 

 perhaps represents coagulated mucus and cellular debris, to 

 which the whitishness of the papillaj must be due. Finer 

 perceptory hairy processes, which are without any cytoplasm, 

 project outside, forming a short hairy microscopic collar 

 round the seta. 



