The nervous system in the Cestode Moniezia expansa. 369 



membrane is very thin, often almost indistinguishable from the 

 granular cytoplasm that surrounds the nucleus, but it is not of uniform 

 thickness, small thickenings appearing without regular arrangement 

 upon its inner surface. The cytoplasmic contents are gathered about 

 the nucleus into a dense granular mass, from which threads and films 

 of spongioplasm radiate through the hyaloplasm to the cell wall, thus 

 producing more or less of a stellate appearance (PI. 24, Figs. 21 — 24,26). 

 From these anterior ganglia are given off nerve fibres that are distri- 

 buted to the anterior end of the scolex, to the acetabula, and to the 

 musculature of that region. I was not able to discover any regularity 

 in the number or distribution of these branches, such as Niemiec (1885) 

 has shown; there was instead a very loose, poorly defined, set of 

 nerves that crossed and recrossed one another in a very confusing 

 manner. 



Niemiec (1885) has described in Taenia coenurus a nerve ring 

 lying anterior to the acetabula, but having eight ganglia — instead 

 of four, as in Moniezia — placed in pairs, one pair in each quadrant 

 of the scolex. In Taenia serrata he also found an anterior nerve 

 ring, but without any pronounced ganglionic enlargements. 



In Moniezia expansa^ as in Taenia coenurus^ there are eight 

 distinct longitudinal nerve trunks that pass backward from the anterior 

 nerve ring, two arising in each quadrant of the ring, but unlike Taenia 

 coenurus these large pairs of nerve trunks have their origin in the 

 posterior surface of each of the four anterior ganglia, one on the ex- 

 ternal edge of the ganglion, the other on its internal edge. The one 

 arising on the inner edge which is the larger, passes to the cephalic 

 ganglion of its own side, and in passing backward approaches 

 toward the chief axis of the worm ; while the one that arises from 

 the outer edge runs posteriorly parallel to the surface, becoming 

 either one of the two dorsal or two ventral longitudinal nerves. (The 

 further description of these outer nerves will be taken up after an 

 account of the inner nerves and of the position of the nervous apparatus 

 immediately connected with them.) 



The two inner nerves arising from the ganglia of the right side 

 of the animal converge until they meet at a point not far behind the 

 division of the excretory tube into its dorsal and ventral branches, 

 where they at the same time unite with the right anterior horn of 

 the cephalic ganglion (PI. 21, Figs. 1 and 2). The nerves of the left 

 side have similar relations. These nerves may be called the cephalic 

 connectives, being simply compact bundles of nerve fibres without 



