The nervous system in the Cestode Moniezia expansa. 375 



regularity as to their arrangemeut. In Vom Rath preparations the 

 nuclei of some of these cells are deeply stained and each contains a 

 very dense nucleolus {vin.cl, PI. 25, Fig. 29 and PL 24, Fig. 15); 

 whereas, in other binding cells of the same preparation the nucleus 

 is unstained, while the nucleolus is deeply stained. Granular cyto- 

 plasm is usually collected around the nucleus and passes thence in 

 radiating and sometimes branching strands to the periphery of the 

 cell, giving the whole a stellate appearance. These are probably 

 modified mesodermal cells. 



Along the course of the lateral nerve between the anterior and 

 posterior lateral ganglia there are ganglionic cells, some of them in 

 the nerve itself others outside the nerve. These ganglionic cells are 

 mostly bipolar or multipolar, but in one case (PI. 25, Fig. 30 cl.gn), 

 two unipolar ganglionic cells were found lying outside the nerve and 

 sending each an axis cylinder into the nerve. In one case the fibre 

 shortly left the nerve, and, passing outward, terminated in a cup- 

 shaped structure, which enveloped one end of an ellipsoidal, hyaline, 

 structureless body, the other end of which was enveloped by a similar 

 cup-shaped structure formed by the end of another nerve. I have 

 observed this structure in several methylen-blue preparations, however 

 I am inclined to believe that it is due to some post-mortem change 

 caused by the reagents used. The ganglionic cells which lie in the 

 nerve substance (PI. 24, Fig. 15 cl.gn) are usually small and of the 

 multipolar type, and are frequently seen to give rise to nerve fibres 

 which emerge from the nerve. 



The lateral nerve is single throughout its entire length, and no 

 trace of additional lateral nerves, such as have been described in other 

 Cestodes, has been found. 



In the posterior part of each proglottis the lateral nerve becomes 

 enlarged by the aggregation of ganglionic cells, forming what I have 

 called the posterior lateral ganglion (PI. 22, Fig. 6 gn.l.p). It lies 

 close to the longitudinal excretory tube (PI. 25, Fig. 28 and PI. 26, 

 Fig. 31), and nearly opposite the point whence the transverse ex- 

 cretory tube .is given off. The ganglion is ellipsoidal, its antero- 

 posterior diameter being greater than its dorso-ventral diameter, 

 which, in turn, is greater than its dextro-sinistral diameter. It varies 

 considerably in size, being largest in those proglottides which contain very 

 young embryos while in the older proglottides it undergoes degeneration. 



From this ganglion there arise besides several smaller nerves, 

 two large ones, one from its dorsal, the other from its ventral surface ; 



Zool. Jahrb. XUI. Abth. f. Morph. 25 



