MUSEUM OF COMPARATIVE ZOOLOGY. 177 



caliber of the opening (Figs. 10, 56), and thus to facilitate the passage of 

 the egg mass. The hypodermis can hardly be followed around the bend 

 under the infolded cuticula. If it exists there, it is certainly a very 

 much attenuated layer. I do not think that the elongated cells of the 

 bulb can be regarded as modified hypodermal cells. 



VI. Discussion. 



1. Dorsal Cells. 



The nature of the dorsal cells is not definitely determined, yet I have 

 little doubt as to their nervous character. The interpretation of them 

 as gland cells (Burger, '91) seems to me untenable for many reasons. 

 The cells do not have at all the appearance of gland cells, there is no 

 trace of any secretion in the cell or its process, nor anything in this pro- 

 cess which suggests even remotely a duct, and finally one finds no con- 

 nection of the stalk with the intestine or with the exterior. Against the 

 possibility that they may be degenerate gland cells, functional in lai'val 

 life, it may be urged that there is absolutely no evidence of degeneration 

 in the appearance of the cells. 



If the positive evidence on the other side be examined, it will be 

 found to be almost equally strong, and in favor of their nervous charac- 

 ter. In the first place, their nuclei are like those of the large ganglion 

 cells in affinity for stains, in the possession of one or two large homo- 

 geneous nucleoli, and in the curious unstained enclosures already 

 described. On the other hand, it cannot be denied that the nuclear 

 membrane is more irregular, and seems to be connected with the fibres 

 of the cell substance, a condition which was not seen in the large gan- 

 glion cells. 



The stalks of these cells certainly resemble nervous processes opti- 

 cally, as well as in their relation to the cell body, and in their termina- 

 tion, which has been considered in detail. Unless one regards the stalk 

 as differentiated into a stainable and a non-stainable portion on account 

 of some unknown difference in the chemical nature of the parts, it must 

 be granted, I think, from the evidence previously produced, that the pro- 

 cess branches at or near its termination in the brain. This branchins: 

 seems to me to be an insuperable objection to the interpretation of these 

 cells as glandular, and indeed to render it almost certain that they are 

 nervous. Their enormous size and extremely fluid contents may be 

 due to the freedom for growth which they enjoy in an unrestricted space, 

 and, in part at least, to osmotic conditions. 



