No. I.] DESMOGNATHUS FUSCA. 265 



spinal ganglia, because the former do not show peripheral and 

 central fibers provided with myelin, neurilemma, etc. If we 

 cannot admit that a portion of this single process of the cell 

 in Desmogiiathus is dendritic or cellipetal in function, then it 

 must follow that the impulse must pass out from its cell of 

 origin toward the periphery, but cannot again take a cellipetal 

 direction in one of these unipolar cells. In these cells the 

 conduction would seem to be cellifugal, and a physiological 

 difference may be distinguished between these and the fusi- 

 form cells, for the latter have numerous processes, and con- 

 duction is probably both cellipetal and cellifugal, though it is 

 worth noting that these processes extend for the most part 

 toward the periphery. 



The third type of cell of the Desmognathus was found only 

 in the oblongata (Figs. 40 and 45); they are larger than the 

 others, and in outline resemble the so-called multipolar cells. 



The various forms undergone by the cells just described, 

 confirmed to a greater or less extent by ontogeny, seem to 

 indicate that the unipolar is the primitive type of the nerve 

 cell in the central nervous system, and that it merges gradually 

 into the fusiform stage; while the pyramidal cell — the highest 

 and most typical form of a nerve cell — " may be imagined as 

 evolved from a fusiform cell." 



Aside from the endyma, nothing comparable to neuroglia 

 cells was noted except in an unsuccessful sublimate preparation 

 where no satisfactory conclusion could be arrived at as to 

 whether the appearance was really a cell or an irregular pre- 

 cipitate. The neuroglia cells described by Sclavunos in the 

 Salamandra maculata and Siredon as having a central process 

 as well as peripheral ones, were not demonstrable in the 

 Desmognathus. I have, however, found such an appearance in 

 the prosencephal of a larval Petromyzon. The cells were not 

 far distant from the ental boundary, and in some cases the 

 central process appeared to project even into the cavity. 



In the myel, many preparations seemed to show a distinct 

 difference of caliber between the fibers of the dorsal and 

 ventral roots, the former being the coarser. In their passage 

 from the periphery to the myel, the dorsal root fibers assume 



