GLANDULAR EPITHELIUM AND DIVISION OF NIJCLEI. 409 



verse section through tail of newt we notice that the epider- 

 mis, whose thickness amounts to O'OSl to 0'094 mm., shows 

 a deep stratum consisting of one or two layers of cells elon- 

 gated vertically to the surface, their nucleus is generally oval ; 

 then follow two to three layers of polyhedral cells, their nu- 

 cleus is generally round, in some instances oval in a hori- 

 zontal direction ; and, finally, one or two layers of flat cells, 

 their nucleus being flattened horizontally and deeply stained 

 in hsematoxylin. The top layer is always very highly refrac- 

 tive, and as such differs in a conspicuous manner from the 

 transparent layers underneath. Some preparations show 

 in some places two such layers of highly refractive cell plates, 

 in others only one, and still in others we see one such layer in 

 the act of detaching itself from the layer underneath. The 

 outlines of the cells, especially those of the middle strata 

 are striated, numerous fine fibrils passing from the substance 

 of one cell into that of its neighbours, prickle cells. In pre- 

 parations obtained from bits of tail hardened in a ^ per 

 cent, solution of chromic acid, these connecting fibrils are in 

 many places of excessive length, the cells, probably through 

 shrinking, having become separated from each other to a 

 much greater extent than is ordinarily seen. And here these 

 fibrils are distinctly seen to pass directly from the reticulated 

 substance of one cell into that of its neighbours, as I de- 

 scribed and figured it of the cells of stratified epithelium in 

 a paper in the April number of this journal. 



Passingly I may mention the numerous migratory cells, 

 with their folded and constricted nuclei, sometimes drawn out 

 in fine filaments ; further, the branched connective-tissue cells 

 with an oblong nucleus, and containing occasionally pigment 

 granules, all these structures being found in the intercellular 

 cement substance of the epidermis. 



The variability of the highly refractive top layer of cells, 

 viz., whether one or two, finds its ready explanation in the 

 fact easily noticed on observing newts* (kept in watei-) 

 for several days, viz. that the cuticle is shed in form of 

 a thin transparent membrane. By keeping several ani- 

 mals in one vessel it is difficult to exactly estimate 

 the rapidity and extent of this process of shedding, but if 

 each animal be kept isolated, it can be observed much 

 easier. 



The following table shows the exact rapidity with which 

 four adult newts shed their cuticle while observed during May 

 and beginning of June, the animals being kept separately in 

 clear water : — 



