The Histogenesis of Cysticercus pisiformis. 215 



at least in some particular instances (p. 210, 211); and it has been 

 possible, moreover, to demonstrate the same method of development 

 at several other places along the nerve trunks. This method of 

 development has been observed in proglottids of Taenia serrata in 

 which the reproductive system was alreadj^ well established. 

 Therefore, one is justified in maintaining- it to be generally true. 

 Such an assumption does not of course exclude the two last 

 hypotheses, but these have already been sufficiently discussed. As 

 will be seen in the discussion of cytogenesis parenchj-ma cells 

 likewise arise from masses of protoplasm elaborated by the paren- 

 chyma network. Hence the question as to the origin of nerve cells 

 from such protoplasmic masses, or from modified parenchyma cells, 

 is of relatively small importance. Whether the elaborated proto- 

 plasm is derived from special cells or from the general parenchyma 

 network, one cannot say. Reasoning by analogy from the customary 

 method of cytogenesis in the larva the latter method seems to be 

 probably the more general one. On the other hand. Fig. 53 shows 

 a single cell as the probable source of the developing nerve cell in 

 that particular instance. It seems probable, therefore, that both 

 cells and general parenchyma network are the source of the neuro- 

 genic protoplasm. ^) The development of the ganglion cells consists 

 in a fibrillation of their granular cytoplasm as described for the 

 nerve fibres, together with the formation of chromatin granules and 

 their collection into a nucleus. Whether there is a continuity of 

 the nerve fibrillae with the nuclear network cannot be said with 

 certainty. Such apparent continuity has been seen in several cases, 

 but absolute proof thereof is lacking. 



"Myoblasts", or Neuro- muscular Cells and Peripheral 



Nerves. 



The development of these cells in situ from pre-existent paren- 

 chyma cells has already' been discussed. I have observed one 

 very probable instance of the development of a neuro-muscular cell 

 from a granular protoplasmic mass elaborated by the parenchyma 

 network. 



I have already acknowledged my inability to settle the question 

 as to the former method of origin for some of the ganglion cells of 



1) Since the network is in reality a continuation of the parenchyma 

 cells this question is of minor importance. 



Zool. Jahrb. XXVI. Abt. f. Anat. 15 



