258 FISH. [Vol. X. 



tracts while the cells have been practically ignored. The 

 older methods are poorly adapted for demonstrating cellular 

 morphology, and the apparent simplicity of the cells did not 

 merit a very extended description. Reissner, Stieda, Bellonci, 

 Osborn, and several others have contributed very largely to the 

 knowledge of the neurology of this group, considering the 

 methods at their disposal. Oyarzun (39), Lavdowsky (25), and 

 Sclavunos (51) by the application of the silver nitrate method 

 have added information that is new and valuable. Oyarzun 

 confined his investigation to the cerebrum of the frog, sala- 

 mander, and Triton, and obtained essentially the same results 

 in them all. He distinguishes two quite different kinds of 

 cells : first, the endymal or those lining the cavities of the 

 brain, which send off a process toward the periphery ; this sub- 

 divides and forms a dense network. He concludes that this 

 net or fibrous interlacement forms the supporting tissue or 

 chief mass of the molecular layer. The second kind of cell is 

 found at any level in the cell layer, but never directly bounding 

 the cavities like the endymal cells. They are multipolar and 

 send out numerous processes in an ental and tangential direc- 

 tion, while often from the ental side of the cell a smooth process 

 was noted passing mostly in an ento-caudal direction (the axis- 

 cylinder). A general analogy is noted between the cells and 

 their processes and supporting substance, and the conditions 

 existing in the early embryonic stages. 



Lavdowsky (25) treats of the my el of certain mammals and 

 Anura, especially of the neuroglia and nerve cells. In the myel 

 of the frog he indentified four kinds of glia cells : First, the 

 wedge-shaped endymal cells, the blunt end being next to the 

 cavity and the long peripheral process projecting from the 

 opposite end. Secohd, large branching cells, which resembled 

 pigment cells, sending off processes peripherally through the 

 alba to connect with the "pin" fibers of Stieda from the pia. 

 The third form are the so-called "pin " fibers which according 

 to Lavdowsky's view are not fibers at all, but cells drawn out 

 into the appearance of fibers. The fourth kind is represented 

 by a conglomerate of small cells situated just ventral to the 

 myelocoele. With regard to the nerve cells, he finds no essential 



