352 ^^6 Philippine Journal of Science 1913 



trie cavity they are found in large numbers, the large endoderm 

 cells containing from 3 to 10; in the mass of glandular endo- 

 derm cells surrounding the proximal aperture of the hypostome 

 and in the endoderm of the hypostome itself they are not so nu- 

 merous. Their presence in such enormous numbers in the ten- 

 tacles is without doubt due to the fact that there they receive 

 most freely the light which is so essential for the carrying on of 

 the photosynthetic processes. They are often found dividing 

 into 2 and more rarely into 4. This division is particularly 

 frequent among those included in the ovum as noted by Mangan 

 ('09). 



SUMMAEY 



Eudendrium griffini is a very distinct species. Its most im- 

 portant distinguishing characteristics are the large number of 

 distally directed tentacles, the long and slender hydranth boUy, 

 the small size of the hypostome, the presence of but 2 male 

 gonophores to a hydranth, and the deposition of the ova on the 

 pedicels. 



The terminal hydranths of both male and female hydrocauli 

 are sterile, making it probable that we have two types of zooids, 

 nutritive and sexual, or at least a distribution of function. In 

 older colonies they are attenuated, and in various stages of de- 

 generation, due probably to their being the original and oldest 

 individuals of the hydrocauli. 



As a result of the early atrophy of the female hydranths, the 

 gonophores relax and allow the ova to hang down beside the 

 pedicels, in which their weight makes a depression and where 

 they become attached by their mesoglceal envelope and probably 

 remain during their early developmental stages. 



Great numbers of zooxanthellse inhabit the endoderm cells 

 of the ccenosarc, gastric cavity, and tentacles, lying in the bases 

 of the cells next the mesogloea. They are found in the process of 

 division. They are not so numerous in the ccenosarc, but in the 

 large endoderm cells of the tentacles they form a closely packed 

 layer just within the peripheral walls, as many as 30 or more 

 being found in a single cell. No nuclei of included cells or 

 pseudo-cells are found in the ova of E. griffini, and, inasmuch as 

 the zooxanthellse show a marked resemblance in form and posi- 

 tion to the included nuclei and pseudo-cells figured by other 

 authors, it seems very probable that the spherical bodies found 

 in hydroid ova and described as included nuclei or pseudo-cells 

 were in reality zooxanthellse taken in by the ova with absorbed 

 endoderm cells. 



