PRIMITIVE PORES OF POLYODOX SPATHULA 463 
slender. Whatever the shape of the basal cell, the nucleus lies 
in the distal region of the cell. The layers between these two 
extremes present the usual intermediate cell-forms of a many- 
layered epithelium. In well stained preparations all the cells, 
excepting the outermost flat cells, have a blue to blue-gray tint. 
The nuclei stain more deeply in spots but appear quite clear and 
present a rather open chromatin network in which one can usually 
recognize a distinct nucleolus, using the term in a morphological 
sense only. The cells of the outer two or three layers stain more 
deeply than the rest, appear much denser and have dense, deeply 
stained nuclei, which appear like slender rods. This difference 
in structure and affinity for stains makes the outer layers, when 
seen under a moderate power, appear like a limiting membrane. 
Just within the mouth of the pit this apparent limiting membrane 
disappears, the number of layers of cells becomes reduced and 
gradually, though rapidly, falls to two near the bottom of the pit. 
At and wuthin the mouth of the pit the surface cells frequently 
present finger-like processes which, as a rule, slant obliquel}^ 
toward the mouth of the pit. In color and consistency^ these 
processes frequently remind one of the surface cells of the skin. 
They represent not a special structure but merely the loosened 
overlapping edges of the cells. Xear the bottom of the pit these 
processes are usually wanting, though shorter, more delicate and 
less deeply stained processes may be present on the cells next to 
the edge of the differentiated bottom epithelium. Aside from the 
appearance due to the overlapping of the cells, the thickness and 
plane of the section, these processes appear to be artifacts due to 
partial maceration or imperfect hardening or after treatment. 
They appear in greatest profusion in preparations whose general 
appearance reminds one of poorly preserved material. In well 
perserved material, carefully sectioned and carefully mounted, 
the fingerlike processes are not prominent and not infrequently 
are absent altogether. On the other hand they are seen in some 
preparations that otherwise appear well preserved. It is not at 
all impossible that the conditions within a pit affect the ordinary 
surface eipthelium much as warm water acts on the skin of the 
dead fish. The mucous and other conditions may cause stagna- 
