500 A. B. DAWSON 
flattened (fig. 11). The nuclei are present in all layers. In 
Siredon pisciformis a stratum corneum is developed on the tip 
of the snout as well as on the extremities of the appendages 
(Carriére, ’85; Paulicki, ’85). 
In the 10-cm. larva studied, an interesting condition was noted 
on the toes. Here the cornification involved the ventral surface 
only, while the dorsal surface possessed a typical cuticular margin. 
Passing from the dorsal to the ventral surface, no sharp line of 
distinction between the two conditions could be observed. The 
cuticular cells became gradually more flattened and their margins 
correspondingly thinner, till a stage was reached where the 
cuticular structure had entirely disappeared and it was impossible 
to distinguish between the two types of cells. 
D. Club cells 
The ‘club’ cells, so conspicuous in many preparations on 
account of. their number, size, and staining qualities, are the 
same as the ‘Schleimzellen’ first described by Leydig in sala- 
mander larvae and Proteus. They have, since been reported 
as present in many other Amphibia and have usually been referred 
to as cells of Leydig. Pfitzner (’79, ’80; salamander larvae) 
and Carriére (’85; Siredon pisciformis) have followed their early 
development. They arise by a metamorphosis of cells in the 
stratum mucosum and later multiply by indirect division. 
Mitoses in these cells have also been reported by Paulicki (’85), 
Cohn (’95), and Prowazek (’01). 
1. Morphology. In Necturus, according to Eycleshymer and 
Wilson (’10), these large ‘mucous’ cells appear in the 11-mm. 
embryo at the time the epidermis becomes two-layered. In 
adult animals the cells attain a considerable size, having, when 
seen in perpendicular section, an area six to eight times larger 
than that of the ordinary epithelial cells: They are club-shaped 
with their small ends resting on the dermis. They occur at 
varying intervals through the epidermis, in many regions lying 
uniformly close together (fig. 14). The epithelial cells in their 
immediate neighborhood always have the appearance of being 
displaced under a considerable pressure. In many cases where 
