VIII, D, 5 Light: Mo7-phology of Eudendrmm 341 



The male hydranths of E. maldivense Borradaile ('05) which bear 

 one or several gonophores and those of E. griffini which usually 

 bear two are examples of the second condition, where we have 

 few gonophores to a hydranth and little or no signs of shortening 

 or atrophy. 



At the base of the hydranth and lying just above the ter- 

 mination of the perisarc is a region in which the ectoderai cells 

 are very large, stain heavily, and contain a considerable amount 

 of granular material. This region is separated from the upper 

 portion of the hydranth by a groove, most conspicuous in hy- 

 dranths not fully grown. This region of large ectoderm cells 

 together with the groove and another region of enlarged ectoderm 

 cells just above the groove constitute a "sense ring" similar to 

 that spoken of by Weismann ('81), Congdon ('06), and Warren 

 ('08) for E. racemosum, E. capillar e, E. hargitti, E. parvum, 

 and E. angustum. The cnidophore described by Weismann ('81) 

 and mentioned by Congdon ('06) was found in only two speci- 

 mens of E. griffini, both fertile females, and seemed to be in the 

 nature of an aborted gonophore. 



The hypostome, which is very small in proportion to the size 

 of the hydranth, arises from the center of the distal end and 

 is usually hidden by the tentacles. When extended, it is very 

 slender with a very small aperture, but when expanded it is 

 very short with everted lips and an aperture wider than its 

 greatest diameter below the aperture. In most species of Euden- 

 drium the hypostome is large and conspicuous, but in E, griffini 

 the opposite is true, giving the hydranth an appearance quite 

 different from that of the typical species of the genus. 



The tentacles are from 50 to 70 in number. This is almost 

 double the number possessed by any known species of the genus, 

 the nearest approach to this number being found in E. hargitti 

 Congdon which has from 35 to 42 tentacles. The tentacles arise 

 in 2 or 3 closely packed rows, and in preserved specimens ex- 

 tend almost directly forward, forming a dense fringe which com- 

 pletely hides the hypostome. The tentacles have a roughened 

 appearance due to the irregularity of the ectoderm, and in cleared 

 specimens have the characteristic segmented appearance of 

 hydroid tentacles. They are armed, particularly in their distal 

 portions, with numbers of nematocysts in groups of 2 or 3, 

 giving them a spiny appearance. 



Gonophores. — The female gonophores are found in regular 

 verticils on the hydranths just above the sense ring. They are 

 of the typical streptospadicious form of the genus, being very 

 similar to those described and figured by Agassiz ('62) for 



