The Histogenesis of Cysticercus pisiformis. 197 



smaller granules of the same. This mass is surroanded by a clear 

 area in Avhich may be seen, tho not distinctly, a few flbrillae not 

 shown in the figure. The nucleus is surrounded by a distinct, 

 darkly staining membrane; but, while the cell outline is perfectly 

 sharp, there is no apparent membrane limiting it. In an adult larva, 

 the development of the sub-cuticular „myoblasts" may be followed 

 thru différent stages in passing from the embryonic bladder wall to 

 the adult tissue in the neck region. In the former region where 

 the sub-cuticular muscles are a part of the general parenchyma 

 sjmcytium, there are found occasional elongated, narrowly spindle- 

 shaped cells with their long axes perpendicular to the surface of 

 the larva. Their peripheral processes are continuous with the sub- 

 cuticular muscles, while their central ones form part of the par- 

 enchyma syncytium. They are in direct union, moreover, with the 

 future sub-cuticular cells. Here, as in the previously described neuro- 

 muscular cell, the cytoplasm is finely fibrillated and the only change 

 apparent in the internal structure of the cell during advancing de- 

 velopment is in the increased density of the nucleus. In its ex- 

 ternal relations, the neuro-muscular cell in its progressive development 

 becomes sharply delimited from the surrounding tissues (Fig. 50). ^) 

 The evidence here presented shows, I think, conclusively that the 

 neuro-muscular cells are developed by a modification of pre-existing 

 parenchyma cells in situ. A comparative study of several cells at 

 this stage makes it appear as highly probable, altho positive proof 

 is lacking, that the cytoplasmic network is in continuity with the 

 nuclear network. This point will be taken up later. 



The t3'pical neuro-muscular cell is spindle-shaped, with two 

 opposite poles (Fig. 50). Bipolar cells have been observed in which 

 one of the polar processes branched shortly after leaving the cell, 

 making the latter practically multipolar, but a cell in which several 

 muscle processes were distinct from their connection with the cell 

 itself has not been observed. ^) ^) As gradual development progresses, 



1) "Whether all connection with parenchyma and sub-cuticular cells is 

 lost or not cannot be said with certainty. It seems possible at least that 

 some of these cells may innervate the sub-cuticular cells, but this point 

 has not been determined. 



2) An exception to this last statement is presented by the neuro- 

 muscular cells in the suckers. 



3) In the embryonic condition the neuro-muscular cells have frequently 

 three processes (Fig. 43). Two of these probably fuse for some distance 



