288 ERNEST WARREN. 



which happened to terminate in a hydrocauhis {hij.) and 

 hydranth [h.h.). The layer shown solid {end.) is the endoderm, 

 ex. are the endodermal canals, c.e. the common ectoderm in 

 which the canals are embedded, h.hy. is a branch coming* off 

 from the hydrorhiza, and it shows a fork in the endodermal 

 canal at e.c. 



Fig. B is a. cross-section through the hydrorhiza, and shows 

 three endodermal canals {e.c), surrounded by a common 

 ectoderm which contains three large nematocysts {l.n.). The 

 perisarc {j^-), consisting of loose laminse, is well seen. 



The endodermal canals do not seem to necessarily arise as 

 direct tubular outpushings from a main canal, but sometimes, 

 at any rate, they appear to originate as solid strings of endo- 

 derm cells, which split off from the main canal, and in which 

 a cavity ultimately becomes hollowed out. Occasionally the 

 perisarc dips down into the ectoderm between the forks, so 

 that for a distance of j mm. or so there may be two perisarc 

 tubes (fig, C). A cross-section through ab. is shown at fig. D. 



Systematic Position. — This hydroid appears to be unique in 

 the nature of its tentacles. In P e n n a r i a, C 1 a d o n e m a, and 

 Stauridium the hydranth is provided with both capitate 

 and filiform tentacles, but the latter are arranged in a definite 

 basal verticil. 



In Asyncoryne the filiform tentacles are scattered, and 

 they also possess an unusual moniliform structure, and 

 terminate in a kind of rudimentary capitulum. The structure 

 of the tentacles recalls that of the marginal tentacles of the 

 medusa of Cladonema and Syncoryne. 



In the nature of the tentacles, AsyncorjMie shows affinity 

 to Cladocoryne. In Cladocoryne there is a verticil of 

 simple capitate tentacles around the mouth, just as in Asyn- 

 coryne, while over the body there are arranged a number of 

 pinnate capitate tentacles. The moniliform tentacle of 

 Asyncoryne may perhaps be regarded as intermediate in 

 nature between an ordinary filiform tentacle and a pinnate 

 capitate one. 



In Coryne and Syncoryne we have scattered capitate 



