62 On Conjoined Ejpithelium. By S. Mariyn. 
across on a plank. In some cases, however, pointed teeth may be 
seen at touching cell-margins, as in Max Schultze's original plate. 
But it is an illusion, in my opinion, to see in this appearance a true 
second set of interlocking teeth, the outlines of which correspond 
precisely with the first. Eather let it be granted that prickles are 
broken bands of union in all cases, as we know they are in (e. g. a, 
Eig. 2), and then the whole thing becomes intelligible. In a 
microscopic preparation thin enough to be seen well with 1000 
diameters, most cells are partly isolated, and consequently broken 
bands, i. e. prickles, abound, and those near the outer margin of the 
cells lie as detached teeth touching from each cell-wall, or even 
interlocking in some instances. Meanwhile the cell-margins of 
real contact deeper down are united by unbroken bands. 
So much for the prickles; and next as to the "furrows," 
" reefs," " ribs," or " ridges " (see Fig. 1, a, and Fig. 2, c). I con- 
fess that at present the only explanation which occurs to me is 
founded on an insufficient number of observations. As a conjecture 
supported by some instances, I would suggest that these are 
stretched hands often broken off at one end, and lying parallel on 
the cell-wall. They are beautifully seen with careful oblique 
illumination under high powers. 
This peculiar cell-structure which we have been describing may, 
then, be supposed to originate in this sort of way. In the lowest 
cell-layer of epithelium there are found the newly grown, long, 
vertically placed cells, side by side in contact. When these have a 
somewhat permanent character, as in many fishes, the next layer of 
cells consists of spheroidal cell-forms which have resulted from 
division or budding, and consequent " fissiparous " multiplication or 
budding of a new progeny. In all this there is a tendency of 
dividing cells to remain, at points, united by threads of formed 
material of hard cell- wall ; e. g. amongst these very layers are 
often found large and branched pigment-cells united by long 
delicate threads. Thus I imagine the cells of rete mucosum, in 
multiplying originally by subdivision, retain numerous points of 
incomplete severance, and these points of cohesion are dragged out 
and become the uniting bands. These, when severed by any acci- 
dent, assume the characteristic form of " prickles." In the normal 
ascending series, these cells, becoming older and flatter, lose all 
surface connection, and in the cuticle are simple polyhedral horny 
blocks. The uniting agency of these cells is a firm one ; for in a 
scraping from a tumour section, as noticed by Kanvier, they almost 
always hold together strongly in groups. It is a firmer union than 
I should expect from any interlocking teeth, but of course one 
which would naturally result from uniting bands. 
Lastly, as to the pathological anatomy. The primary meaning 
of the presence of these cells is an abnormal formative activity of 
the lower cells in the rete mucosum ; and the occurrence of rib and 
