548 
H. V. WILSON 
Two hours after cutting. The cells at the surface are now more 
uniformly flattened than they were an hour earlier. A group 
of the superficial cells is shown in fig. 6. 
Five hours after cutting. The surface is now occupied by a layer 
of thin, flattened, coarsely granular cells or cell areas connected 
by a complex network of fine intercellular strands (fig. 7). The 
cells areas are mostly uninucleate but may include two or even 
three nuclei. The areas have no precise boundaries but merge 
gradually into the intercellular network. On focussing below 
the surface layer, coarsely granular mesenchymal cells come into 
view. These have slender processes and are freely interconnected 
forming a coarse open network (fig. 8, m.c). This open network 
of coarsely granular mesenchymal cells constitutes the body of 
the developing dermal membrane. In it spaces which doubtless 
represent pore canals have already appeared. One such is shown 
in fig. 8 (p.c). The mesenchyme cells bounding it, and which 
doubtless become the lining epithelium, do not yet form a con- 
tinuous wall. Above the developing pore canal the epidermal 
layer, p.7n., is shown as it appears at the upper focus. 
Twelve hours after cutting. The surface is now occupied by a 
continuous epidermal membrane in which the cells that have fused 
are still distinguishable (fig. 9). The area round each nucleus 
or group of two or three takes a deeper stain and appears as a 
fineh^ granular, vaguely delimited area containing a good many 
of the coarse granules that characterise the fusing cells in earlier 
stages. Between these areas the epidermal membrane is a thin 
continuous sheet which in places appears reticular (alveolar) and 
in other places more fibrillar. In this thin sheet one sees here 
and there a few of the coarse granules which seem to be lodged, 
in cases at least, at the nodes of the reticulum. The sheet exhib- 
its small perforations of varying size, sometimes twice as large 
as that shown in fig. 9 (per.). Possibly these are the beginnings 
of pores, although I was not able to observe that they always lay 
'over pore canals. In a regenerating dermal membrane at this 
stage groups of well formed pore canals are found here and there 
(fig. 9, p.c). In the preparation shown in fig. 9, the pores are 
open. 
