IRREGULAR CELLS IN SPINAL CORD OF FISHES ae 
SUMMARY 
1. Cells homologous to the large irregular glandular cells of 
Dahlgren in the skate are present in the large majority of fishes. 
Of thirty genera examined the Dahlgren cells were found in 
twenty-six. They have not been found in any other group of 
animals. They are always located (when present) in the posterior 
portion of the spinal cord. 
2. Morphologically, many gradations are found. In some of 
the fishes the cells, though somewhat larger, still bear some resem- 
blanece to nerve cells, the nucleus being almost spherical or 
slightly lobulated and containing one plasmosome, as in the 
mackerel. In other fishes, as in the goosefish and butterfish, 
the nucleus is more lobulated with two or three plasmosomes 
often present. In others, as in tautog, sandshark, sting-ray, and 
dogfish, the cells are larger and the nucleus still more lobulated. 
In some a few vacuoles containing precipitate or secretion are 
sometimes found associated with the cells. The extreme size 
is reached in the cells of the flounder and skate. In addition 
to the enormous size of cell and nucleus, a large amount of granu- 
lar secretion is also usually present in the skate with occasional 
vacuolation of the cytoplasm. In the flounder a very few vacu- 
oles containing granular or thread-like precipitate may be found 
occasionally associated with the cells. 
3. The cells have been found in elasmobranchs, teleosts, and 
ganoids. They are relatively larger in elasmobranchs than in 
teleosts (with the exception of the summer flounder) and ganoids. 
4. Vacuoles and secretion material are not present to any 
great extent in any of the fishes other than the skate. Small 
amounts of fine granular material have been found associated 
with the cells of the flounder, sandshark, shark-sucker, scup, 
menhaden, and dogfish. Secretion granules of large size, 
however, are typical of the skate cells alone. In none of the 
other forms, therefore, is there evidence of marked glandular 
activity. 
5. In size of cell, lobulation of nucleus and secretory activity 
the Dahlgren cells of the skate represent the most extreme type 
