The nervous system in the Cestode Moniezia expansa. 37 ^ 



as in the other ganglionic cells of this animal. Where the nerve fibre 

 joins the cell there is an accumulation of granules similar to that 

 about the nucleus (PL 24, Fig. 18). The anterior and external horns 

 of the cephalic ganglia have but few ganglionic cells, being for the 

 most part composed of nerve fibres. 



Although I am not yet prepared to give a detailed account of 

 the path taken by the nerve fibres through the cephalic ganglion, I 

 have to some extent followed their courses and give what I believe 

 to be the paths of the principal groups of them. There is a large 

 bundle of fibres (PI. 22, Fig. 8 B\ which seems to arise from the 

 central ganglionic mass of either side, and to pass through the posterior 

 part of the transverse commissure into the ganglion of the opposite 

 side. The bundle here traverses the posterior part of the ganglion, 

 curving around behind the ganglionic core, and emerges through the 

 external horn to enter the lateral nerve of the side opposite that in 

 which it arose. This bundle is joined just before it passes through 

 the transverse commissure, by a smaller bundle (PL 22, Fig. 8 D), 

 which enters the cephalic ganglion through its anterior horn, probably 

 arising from the two "anterior ganglia" of the same side of the scolex. 

 A third bundle of fibres arising from the anterior ganglia of each 

 side enters the cephalic ganglion of the same side through its anterior 

 horn, passes along the anterior border of this ganglion near its sur- 

 face and finally emerges through its external horn to enter the lateral 

 nerve of the same side of the scolex in which it originated. There 

 are also several other smaller distinct bundles of nerve fibres in the 

 body of the cephalic ganglia, the most conspicuous one being a bundle 

 that traverses the anterior part of the transverse commissure con- 

 necting the central ganglionic cells of one cephalic ganglion with 

 those of the other. 



The external horn of the cephalic ganglion is enlarged where it 

 joins the lateral nerve, and from this enlargement arise several small 

 nerves that are distributed to the acetabula and to the muscles that 

 operate them. From this enlargement there also arise two broad 

 bands of nervous tissue, one from its dorsal, the other from its 

 ventral surface. The former passes dorsad of the dorsal excretory 

 tubes, the latter ventrad of the ventral excretory tubes, to enter the 

 corresponding regions of the cephalic ganglion of the opposite side 

 of the body. These are respectively the dorsal and ventral cephalic 

 commissures (PL 21, Figs. 1 and 5 corns, d', corns, v'). These com- 

 missures are thin bands of loosely arranged nerve fibres, which in 



