310 CARL CASKEY SPEIDEL 
skate. It was thought that it might be of interest in this con- 
nection to see whether or not the administration of pilocarpine or 
stimulation with electricity would have any effect in stimulating 
the cells. Accordingly, a solution of pilocarpine hydrochloride 
(0.1 per cent) was injected into each of four flounders by way of 
the peritoneal cavity and by way of the vertebral canal. This was 
allowed to act for from ten to fifteen minutes. Examination of 
these animals showed that no marked increase in granular se- 
cretion or in vacuole formation had taken place. Electrical 
stimulation of the spinal cord of each of four animals gave a 
similar result. If the Dahlgren cells of the flounder are at all 
glandular in nature they are certainly very sluggish, far more so 
than the homologous cells in the skate. 
It has already been pointed out in a previous paper (2) that 
’ the conclusion that the cells of Dahlgren in the skate were of 
glandular nature applied only to the skate. At that time only 
a few kinds of fishes had been examined and the appearance of 
homologous cells in these forms did not warrant the conclusion 
that they were glandular in these other forms. It seems to me 
that the structure of the cells from a comparative standpoint 
suggests a series of transition stages from primitive nerve tissue 
to glandular tissue. In the skate the cells are markedly glandu- 
lar. In the cells of the barndoor skate, Raia laevis, a very large 
amount of granular secretion is elaborated; in the winter skate, 
Raia ocellata, and the Italian species, Raia punctata, there is 
not quite so much produced; while in the spiny skate, Raia 
radiata, and the summer skate, Raia erinacea, still less secretion 
material is to be found. In the flounder, shark-sucker, dogfish, 
sandshark, and menhaden the cells seem to have only a slight 
glandular activity. In the other forms no secretion material at 
all was seen. 
Examination was also made of the spinal cord of the lamprey, 
Petromyzon, the American newt, Diemyctylus, the mud-puppy, 
Necturus, and of the ventral nerve cord of the lobster, Homarus, 
and the horseshoe crab, Limulus. In none of these were cells 
found that were homologous to the Dahlgren cells of the fishes. 
