VIII. D, 5 Light: Morphology of Eudendriuni 347 



to form a mass of very long, deep-staining, gland cells about 

 160 nix in maximum length and exhibiting the bulging shape 

 characteristic of gland cells. These cells often contain one or 

 more zooxanthellae at their proximal end, sometimes one or two 

 near their distal end, and numerous vacuoles and deeply staining 

 material in several forms, such as small spheres, large spheres, 

 granules, spindles, etc. They show very little, if any, traces 

 of mucus by the toluidin blue test. The endoderm cells change 

 rather abruptly from these very long, slender, dark-staining cells 

 to the smaller, clearer cells of the passage from the hypostome to 

 the gastric cavity and then to the slender closely packed cells 

 of the hypostome. These endoderm cells of the hypostome are 

 very characteristic, having their long axis at right angles to 

 the long axis of the hypostome, which gives them a columnar 

 appearance. They have very well-defined cell walls and distinct, 

 but small, nuclei. They contain irregularly placed masses of 

 very deeply staining granular 

 material, and many of them, 

 particularly toward the distal 

 end of the hypostome, have 

 densely staining areas com- 

 posed of small vacuoles with 

 very dense protoplasm between 

 them (Plate II, fig. 3). 



The endoderm extends into 



the tentacles as a solid core of ^"=- *■ Transverse section of a female gonophore 



and egg irom Eudertdrium griffini. 



large disk-shaped cells. These 



cells average 19 /^^ in diameter. Their pheriphery is lined 

 with zooxanthellae to the number of 25 or 30 which gives them 

 a very characteristic appearance in sections or in surface view. 

 The nuclei of these endoderm cells are situated in the center 

 of the cell with radiating fibers of dense, deeply staining proto- 

 plasm (Plate II, fig. 2). This is best brought out in sections 

 stained with Bismarck brown. These nuclei show irregular 

 nucleoli, and take a rather light but diffuse stain. 



Gonophores. — The ectoderm of the female gonophore, which 

 is, of course, merely a continuation of that of the hydranth, is 

 considerably thicker than that of the hydranth above the sense 

 ring, being about 16 /ifi in thickness at its thickest point. The 

 cell walls are more distinct, and the protoplasm stains much less 

 deeply than in the hydranth. The ectoderm nuclei are rather 

 small, but are deeply staining. The endoderm cells of the spadix 

 resemble in shape those of the upper ccenosarc, being long and 

 slender, about 35 fi/x in length by 7 fi/i in thickness. These cells. 



