The Histogenesis of Cj'sticercus pisiformis. 223 



leitende Primiti vfibrillen von den Gliafasern. Die Netz- 

 fasern als solche können selbstredend nicht auf lange Strecken in der 

 Längsrichtung verfolgt werden ; ... die leitenden Fibrillen hingegen 

 konnte Apathy auf seinen Präparaten oft sehr lange Strecken weit 

 verfolgen." The weak point about this argument is that Apathy's 

 work was not done on Cestodes, hence his observations do not 

 necessarily hold true for that group. Further, Cohn's answer to 

 NiEMiEc's direct assertion that "in demselben [Balkenwerk] die ver- 

 zweigten Enden der Ganglienzellen verlaufen (und nicht in den von 

 den Balken gebildeten Zwischenräumen)", that "die genannten Zellen 

 sind . . . keine kleinern Ganglienzellen, solche gibt es nicht" is not 

 conclusive. 



A comparison of Zeenecke's figs. 47, 48 and 50 with my Fig. 57 

 will convince the reader that the nerve fibres do take part 

 in the formation of the network. This latter figure was 

 drawn from a section of Cysticercus pisiformis treated by 

 Towee's method. It represents the points of departure of two 

 branches of one of the main lateral nerve trunks. These branches 

 are seen to communicate directly with each other thru a single un- 

 branched nerve fibre, but for the most part fibres from the branches 

 break up on reaching the cord forming a network as shown. In 

 such a complex tangle of fibres as is here represented, it is ob- 

 viously extremely difficult to demonstrate beyond the possibility of 

 doubt the existence of anastomoses between individual fibres. That 

 such anastomoses do exist, however, a careful study of several 

 slides prepared by different methods gives every reason to believe. 

 A branching of the fibres has been positively demonstrated in many 

 instances. Such a branching fibre is shown at x in the above figure. 

 On the other hand, the view of Zeenecke (1895, p. 137), that par- 

 enchyma fibres take no part in the formation of the network of the 

 nerves, is untenable. It has already been shown that parenchyma 

 fibres and cells are present in the developing ganglia. This fact is 

 unquestionable, ^^'hether these two networks are in actual proto- 

 plasmic continuity is uncertain. 



The results of this study of the nervous system may be summarized 

 as follows: The neurons are developed simultaneously at several 

 points. There is no relative migration of cells and the different 

 centers of development are not definitely circumscribed. In the main 

 nerve cords and ganglia the neurons are formed from masses of 

 neurogenic protoplasm elaborated either by certain parenchyma cells, 



