30 Papers from the Department of Marine Biology. 
EXPLANATION OF PLATES. 
ant. h.. .. .. anterior horn of gray matter. prec. d... . precipitate staining dark with iron hema- 
cap....... . capillary. toxylin. 
c.c........central canal. prec. 1... . precipitate staining light in sections stained 
epen.... .. .ependymal fibers. with iron hematoxylin and van Gieson’s 
gl.c.......large gland-cell. fluid. 
gr.........granules secreted by large gland-cell. 1 (bi PARAS Reissner’s fiber. 
men. pr.. ..menix primitiva. sp.a......ventral spinal artery. 
nuc...... .. nucleus. sp.v......dorsal spinal vein. 
Nv. C..... .. nerve-cell. O06. wie hen vacuole. 
pl........ .plasmosome. 2. ........unknown plasmosome-like bodies in nu- 
post. h.. .. .posterior horn of gray matter. cleus. 
PLATE 1. 
Fra. 1.—Cross-section of spinal cord of Raia ocellata. Two of the large gland-cells are present, 
one on each side of the central canal and close to it. In the anterior horn to the right is a nerve- 
cell, a comparison with which will bring out the large size of the gland-cells. Note the peripheral 
distribution of the nucleus of the cell to the right. Photograph «146. 
Fig. 2.—Photograph of a wax reconstruction of one of the large gland-cells of Raia ocellata, 
together with the capillary network about it. The white wax represents the cell, the dark wax the 
capillaries. Four capillaries may be seen. 513. 
Fig. 3.—Photograph of a wax reconstruction of the nucleus of the cell shown in figure 5 from 
Raia levis. Note the irregular lobular structure and the large size. 292. 
Fiaq. 4.—Cell from spinal cord of the goose-fish, Lophius piscatorius, thought to be homologous 
to these cells of the skate. A well-defined plasmosome is present in one of the lobes of the irreg- 
ular nucleus. Plasmosomes were also present in the other two lobes in the sections immediately 
preceding the one shown. Photograph X1177. 
PLATE 2. 
Fia. 5.—A single large cell from spinal cord of Raia levis. Vacuoles and granules are present 
in the cytoplasm. Some of the discharged granules may be seen near the cell. The nucleus, 
apparently multiple, is in reality a single one. A reconstruction of this nucleus is shown in 
figure 3. 1028. 
PLATE 3. 
Fic. 6.—A cell from longitudinal section of spinal cord of Raia punctata, showing many small 
vacuoles in the central masses of the cytoplasm and one large one. Photograph X734. 
Fig. 7.—A cell from a longitudinal section of the spinal cord of Raia punctata, showing about 9 
large vacuoles. The nuclear material is centrally located and the vacuoles are at the periphery 
of the cell. Photograph 734. 
Fic. 8.—A cell from a longitudinal section of spinal cord of Raia levis, showing 2 vacuoles 
containing granules which are about to be discharged. Photograph 531. 
Puate 4. 
Fras. 9, 10, 11, 12, 13, 14.—Cells from spinal cord of a Raia punctata embryo 7.9 cm. in length. 
Successive stages in the early development of the large cells, starting with the relatively undiffer- 
entiated cell of figure 9. Growth of cell and early lobulation of nucleus are well shown. 1210. 
Fies. 15, 16.—Cells from spinal cord of a half-grown skate, Raia punctata, 22 em. in length. 
The cell has become much larger and the nucleus much more lobulated. 1210. 
Fig. 17.—A nerve-cell shown for comparison, taken from the spinal cord of a Raia punctata 
embryo 7.9 cm. in length. 1210. 
Fig. 18.—A cell from spinal cord of the dog-fish, thought to be homologous to these cells of the 
skate. 1070. 
Puate 5. 
Fic. 19.—A cell from spinal cord of Raia ocellata, stimulated with pilocarpine for 5 minutes. 
The central portion of the cell is filled with vacuoles containing precipitate which stains much 
like the cell cytoplasm. The nuclear material is peripherially arranged. Photograph X750. 
Fic. 20.—A cell from spinal cord of Raia ocellata stimulated with pilocarpine for 5 minutes. 
Five large vacuoles and some smaller ones are shown in this section. Photograph 531. 
Fia. 21.—Cross-section of spinal cord of Raia ocellata, stimulated with pilocarpine for 10 min- 
utes. One large gland-cell is present in the anterior horn on the left. Note the heavy, dark- 
staining granules, which are present only on the side of the spinal cord on which the cellis. Much 
more than the normal volume of granular material is present in this section. Photograph X153. 
PLATE 6. 
‘Fic. 22.—Longitudinal section of spinal cord of Raia levis, showing vacuoles, precipitate, and 
granules outside the gland-cells in various stages of development. There are present in this 
section vacuoles precipitate, vacuoles with small and large granules, and granules of various sizes 
