132 LOPHOMENIA SPIRALIS. 



cells are confined almost exclusively to the ventral and lateral walls. The 

 dorsal side in both specimens consists entirely of cells whose entire substance, 

 with the exception of a small basally placed nucleus imbedded in a scant amount 

 of protoplasm, consists of a vacuolated homogeneous secretion staining like the 

 muciparous cells of certain gastropods. It is possible that such a secretion is 

 due to the transformation of products similar to those of the ventral granular 

 cells, but there is no trustworthy evidence that such is the case. 



On each side of the ventral furrow immediately in front of the cloacal open- 

 ing are two indentations of the hypodermis each of which contains not less than 

 fifty needle-shaped spicules that are clearly modifications of the spines produced 

 in the adjacent territory. As is shown (Plate 19, fig. 5) they are directed inward 

 toward the mid line and sections show that multitudes of muscle fibres attach 

 to the diverticulum chiefly on its blind extremity. Among the more prominent 

 of these is a transverse band, another extending outwardly and attaching to 

 the body wall and, most prominent of all, numerous strands that pass in a 

 postero-lateral direction and attach to the body wall slightly behind the level 

 of the cloacal opening. 



In its broader features the nervous system of this species corresponds 

 closely to that of the other species described in this paper. The brain is of the 

 ordinary bilobed type and is placed above the buccal cavity (Plate 6, fig. 5). 

 From it six nerves arise that passing forward and downward probably innervate 

 the buccal and body walls with the attendant sense organs. The relations of 

 the pedal, lateral, and buccal connectives also conform to the usual type. The 

 last named cord is exceedingly difficult to follow owing to its almost exact re- 

 semblance to the dense masses of muscle and connective tissue that accompany 

 it, but with high magnification it may be traced to the elongated ganglia placed 

 at the sides of the radula and a little below it. The commissure attaching to 

 the posterior ends of the ganglia passes dorsal to the radula. No clearly defined 

 subradular organ exists and no nerves or ganglia belonging to this system are 

 present so far as it is possible to judge from the material in hand. 



The lateral cords, holding the customary position at the sides of the animal, 

 pass backward through the body and finally terminate in ganglionic enlarge- 

 ments on each side of the pericardium near the tip of the seminal receptacle. 

 The commissure uniting them passes out from the hinder end of each ganglion 

 and crosses dorsal to the intestine. One or two nerves also pass out from each 

 enlargement, but in the confused mass of muscle they have been traced but a 

 short distance. 



