60 CHAETODERMA ERUDITA. 



columnar cells of greater height than those of the adjoining epithelium. In one 

 specimen killed in vom Rath's fluid the protoplasm of the component cells is 

 much vacuolated or in a very small number contains a granular secretion. Poste- 

 rior to the radula, whose general appearance is sufficiently shown (Plate 29, 

 fig. 8), the pharynx becomes dorso-ventrally compressed, then circular and 

 opens into the stomach. This is a relatively spacious organ with thin unfolded 

 walls that posteriorly become thicker and folded. The relation of intestine and 

 liver are typical and require no description. In the proximal part of the liver, and 

 throughout the major portion of the intestine, there are considerable quantities 

 of organic remains, diatoms, sponge spicules, a few fragments of entomostra- 

 cans, and several chambered Foraminifera whose protoplasm was only partially 

 digested. 



The nervous system of this species is exceptionally clearly defined in one 

 specimen killed in vom Rath's fluid and for this reason has been more thoroughly 

 studied than any other species of the genus described in the present paper with 

 the exception of C. attenuata. The brain is very distinctly bilobed, a deep 

 indentation occurring on its anterior surface. From its lateral and forward 

 borders nerves pass into the precerebral ganglia which in turn send tremendous 

 bundles of fibres to the buccal sensory plate. In some species the connectives 

 to the pedal, lateral, and labio-buccal systems have distinct origins in the brain, 

 but in the present case they are united for a considerable distance (Plate 13, 

 fig. 3). Each of these compound connectives after leaving the brain and pass- 

 ing forward a short distance gives rise to the labio-buccal connective and con- 

 siderably farther on the pedal and lateral connectives become differentiated. 

 The pedal and lateral ganglia are in the usual positions and are united by 

 frequent connectives and commissures. At the points of origin of these nerves 

 there are no verj' clearly defined enlargements though anteriorly the pedal 

 and lateral cords are of large size and gradually taper posteriorly, attaining 

 their average size about the hinder border of the prothorax. As these ganglia 

 diminish in size the connectives and commissures become reduced in calibre and 

 are difficult to follow yet they may be traced here and there throughout the 

 entire length of the animal. 



As in C. alleyiuala a nerve arises from each labio-buccal connective 

 about the level of the forward border of the radula and passing inward and 

 downward joins a small subradular ganglionic mass. In this species the gan- 

 glion shows no indication of being paired. Each of these subradular connectives 

 gives rise to a nerve distributed to the subradular organ and more laterally swells 



