368 WM. L. TOWER, 



mature proglottides , while the ventral pair becomes smaller and is 

 lost in the older proglottides. 



The nervous system of Monieeia is imbedded in the connective 

 tissue of the body without any definite bounding membrane or 

 continuous protective structure. Many of the larger and more im- 

 portant trunks, however, have along their courses cells (cl.viri) of a 

 peculiar character. They are elliptical, about twice as long and half 

 as thick as they are broad, and from each cell there are given off a 

 number of branching processes that run over the surface of the nerve. 

 I believe that these processes serve to bind the nerve elements into 

 a firmer structure, though they are not very close together, and do 

 not form a continuous covering. These ("binding cells") are shown in 

 PL 24, Figs. 15 and 16; PL 25, Figs. 29 and 30, and are somewhat 

 different from the Hiillzellen described by ZERNECKE (1895, p. 137) from 

 Ligula. They occur upon the nerves of the scolex and upon the large 

 lateral nerve trunks. I have not yet found them upon the other nerves. 



1. In the Scolex. 



The nervous apparatus of the scolex consists of 1) the anterior 

 nerve ring with its four ganglia ; 2) the pair of large cephalic ganglia ; 

 3) the connecting bundles of nerves between 1 and 2 and 4) the dorsal 

 and ventral commissures connecting the outer ends of the cephalic 

 ganglia. 



At about one-fifth of the length of the scolex from its anterior 

 end is found that part of the central nervous system which I have 

 called the anterior nerve ring (n.a, PL 21, Fig. 1). The ring contains 

 four ganglia, one in each of the four quadrants formed by the 

 intersection of the sagittal and lateral planes of the scolex, and a 

 little in front of and deeper than the corresponding acetabulum. 

 These ganglia are here designated according to their positions as the 

 anterior dextro-dorsal (gn.a.dx~d, PL 21, Fig. 1), sinistro-dorsal 

 (gn.a.s-d), dextro-ventral and sinistro- ventral ganglia. The bundles 

 of nerve fibres connecting the ganglia with one another constitute the 

 anterior nerve ring. The ganglia contain a moderate number of 

 ganglionic cells, which differ from those of the rest of the nervous 

 system in size. They are small and, I believe, mostly unipolar, 

 although there are a few bipolar and multipolar ones. These cells 

 (PL 24, Figs. 2124, 26) have a clear and relatively large nucleus, with 

 a deeply staining nucleolus; but no trace of a chromatin network or 

 granular structure was observable in the nucleoplasm. The nuclear 



