130 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



fibers arise from each cell, one or two of which enter the 

 longitudinal cords (fig. 8), while the others join some of 

 he neighboring commissures or their smaller branches. In 

 addition, there are often several protoplasmic processes 

 (dendrites) which form a confused tangle about each cell, 

 or passing outward end freely at a short distance. 



Lying along the median dorsal line of the body, and 

 therefore half-way between the main longitudinal nerves, 

 is a nerve cord which extends from the hinder end of the 

 pharynx to the posterior sucking disc. All the commis- 

 sures connecting the longitudinal strands appear to unite 

 with it, and anteriorly it apparently terminates in the first 

 connective, for in no case have its fibers been traced 

 farther forward. From this point backward to the ovary, 

 it includes six or eight large nerve cells similar to those 

 described in the preceding paragraph, whose main fibers 

 traverse the median cord, while the others may extend into 

 the connectives. Posteriorly, it passes into the pedicel ex- 

 actly in the median line. Its caliber, like that of the dorsal 

 pair of longitudinal nerves, is exceedingly small as it enters 

 the stalk, and owing to this fact I have been unable to de- 

 termine accurately the posterior relations of the dorsal 

 nervous system with the ventral. Each of the paired dorsal 

 nerves may be traced to within a short distance of the point 

 of union of the outer and inner ventral cords, but in spite of 

 continued effort their union has never been observed. 



As in the ventral nervous system, the dorsal nerves in- 

 nervate the great superficial muscles or end freely close to 

 the surface of the body, and are therefore probably sen- 

 sory. The ventral musculature is more highly developed 

 than the dorsal; accordingly the motor nerves in this region 

 are relatively more abundant. The excess of nerve termi- 

 nations on the ventral surface is to be explained by the fact 

 that this area rests against the host. 



IX. Visual Organs. 



The eyes, four in number, and having the appearance of 

 small pigment spots, are only partially imbedded in the 



