350 The Philippine Journal of Science wis 



the groove of the sense ring and in a zone just below the distal 

 end of the hypostome and small tear-shaped nematocysts found 

 on the tentacles and now and then in almost all parts of the 

 colony. The large nematocysts average about 17 fifi in length 

 by 6.5 fjLfi in diameter. The thread is not coiled about a central 

 axis as in Hydra, etc., but in a number of coils laid the long 

 way of the capsule (fig. 5). The nematocysts of the zone just 

 distal to the sense ring measure 16 by 6 ju/^. They have long 

 coarse threads which, when discharged, form a fringe around 

 the base of the hydranth. The nematocysts of the hypostome 

 measure from 18 to 19 by 7.5 fifx. Those of the tentacles and 

 those scattered through the ectoderm of the coenosarc are alike 

 in form and size. They are small, tear shaped, about 7.5 /j-fx in 

 length, and taper from a basal width of about 3.5 fift to a point. 

 They can be seen to lie in a clear nonstaining capsule (Plate II, 

 fig. 2, a). 



Zooxanthellse. — Any description of the morphology of E. grif- 

 fini would be incomplete did it not include some mention of the 

 zooxanthellse which are found in large numbers and in great 

 regularity of position within the cells of this hydroid, and, since 

 the literature on this subject is scattered and incomplete and 

 the resemblance which these algae often show in form and 

 position to cell nuclei is apt to cause confusion, I give a short 

 description of those found in E. griffini and a comparison with 

 those found in Millepora. 



Zooxanthellse are found living symbiotically within the cells 

 of many of the lower marine and fresh-water animals, partic- 

 ularly in the phylum Coelenterata. They usually give a green, 

 yellow, or brown color to their hosts. In the case of E. griffini 

 they give the hydroid a sepia-brown color, which fades in the 

 preservative to white or faint yellow. Mangan ('09) in 

 describing the zooxanthellse of the medusae and ova of Millepora 

 says : 



These cells have been figured by Moseley ('81) who was able to examine 

 fresh material. He remarks that they closely resembled those of other 

 hydroids. They contained irregular granules of a bright gamboge-yellow 

 colour, the cell-contents frequently dividing into two, and sometimes, more 

 rarely into four. In the older portions of the colony the pigment was of 

 dark-brown hue. The spherical nucleus exhibited a mass of closely-packed 

 chromatin granules. A pyrenoid was always present, the clear space 

 around which, in most cases, gave the reaction for starch. The pigment- 

 bearing granules, varied in number and size, did not always stain to the 

 same degree, and in some cases had a little starch associated with them. 

 The cell membrane did not respond to cellulose tests. I observed in a few 



