304 CARL CASKEY SPEIDEL 
cells—a syncytium. A study of the embryonic history, how- 
ever, Shows clearly that these cells are not syncytia, but that each 
is developed from a single cell. The chromatin is scattered 
throughout the nucleus in the form of large granules. No definite 
plasmosome is visible. The cytoplasm of a resting cell is homo- 
geneous, but in active stages small and large vacuoles appear. 
Secretion appears in these and finally the contents of the vacuoles 
are discharged in the form of granules of various sizes which 
remain in the tissues of the cord for some time. Often the 
vacuolar membrane does not break as the secretion material is 
discharged, but remains intact and holds the enclosed granules 
together for some time after they have become separated from 
the secreting cell. A section through the lower part of the spinal 
cord of the skate in the region of these active cells will be charac- 
terized by these deeply staining groups of granules which are 
distributed chiefly in the ventral portion of the gray matter. 
This granular material is protein in character and not easily 
soluble. It was found that increase in volume of granular mate- 
rial occurred after stimulation of the spinal cord by electricity 
and pilocarpine, but not after the administration of atropine. 
The evidence, therefore, both morphological and experimental, 
indicated that the large cells of Dahlgren in the skate were 
glandular in nature. The exact function of the secretion, how- 
ever, was still unknown. It was thought that an extensive 
comparative study of homologous cells in other fishes might 
reveal some other forms in which the cells were as unusual as 
they were in the skate, and that more light might be thrown on 
the exact nature and function of the cells. 
eo MATERIAL 
The fishes were obtained for the most part at Woods Hole, 
Massachusetts, during the summer months. ‘Thirty genera were 
studied, comprising most of the common salt-water forms and a 
few fresh-water ones. These include representatives of the 
teleosts, elasmobranchs, and ganoids. Examination was also 
made of the ventral nerve cord of the lobster and horseshoe crab, 
and of the spinal cord of the lamprey, newt, and mud-puppy. 
A complete list of the forms examined follows: 
