218 EoBEET Thompson Young, 



serving thus to loosely bind the nerve fibres together, but they 

 appear in every case similar to ordinary parenchyma cells, in which 

 vievr I agree with Cohn (1898). 



The ganglion cells of the cords are mainly found on the peri- 

 phery of the latter, tho' they are occasionally imbedded in them. 



Three distinct types of neurons are represented in Figs. 54, 55? 

 57, 61 and 64. In one t^^pe the main cell body is heavily stained 

 and apparently entirely composed of chromatin and therefore is 

 equivalent to a nucleus {x Figs. 55, 57 and 61). It is bi-polar 

 and its processes composed of fibrillae. In the second type {x^^ 

 Fig. 55) the cell is likewise bi-polar, with fibrillar processes, 

 but there is a distinct nucleus with nuclear membrane and con- 

 tained chromatin granules — the so-called "nucleoli". The nucleus 

 occupies so large a portion of the diameter of the cell that it is 

 difficult to observe any cytoplasm surrounding it in many cases. The 

 third type, shown in Fig. 54 which represents a ganglion cell from 

 the main lateral nerve cord in a partly developed proglottid, and 

 Fig. 64 representing a few cells from one of the lateral cephalic 

 ganglia of Taenia serrata, I interpret as an embryonic type of cell. 

 It often lacks definite outline and distinct polarity, is composed of 

 granular cytoplasm and contains a nucleus which is sometimes 

 represented by a few chromatin granules (x.^ Fig. 64) with no definite 

 nuclear membrane, sometimes by a definite membrane enclosing a 

 nuclear network (x.^ Figs. 54 and 64). The third type occurs not 

 only in the cephalic ganglia of the larva, but in these ganglia and 

 the ganglia of the main cords in the immature proglottids of the 

 adult, while the other two types are found at scattered intervals 

 along or occasionally within the cords. 



The type of neuron, described by Towee (1900) as typical in 

 Moniezia expansa and figured by Niemiec (1885) in the central 

 ganglion of the scolex of Taenia saginata (see his fig. 8, tab. 21) and 

 by PiNTNER (1880, fig. 11, tab. 3 and fig. 2, tab. 5) on the main 

 nerve trunks of Tetrarliyndms longicollis, has not been found in 

 Cysticercus pisiformis and can only be demonstrated with 

 extreme doubt in Taenia serrata. In one approximately adult pro- 

 glottid of the latter I have found cells such as represented in Fig. 60 

 grouped along the periphery of the main lateral nerve cord. This 

 figure should be compared with the figures of Towee (1900), especially 

 figs. 15 and 20. It will be noted that there are two types of cell 

 represented in my illustration, of one of which only a single cell. 



