MEDUSA. 151 



Aglauropsis and Gossea, which have not an adhesive disc on the tentacles. About 

 the genus Olindias we differ, and it is quite likely that I may be in the wrong. We 

 both examined specimens sent out from the Zoological Station at Naples. I came to 

 the conclusion that the primary (ex-umbrellar) tentacles had not a terminal adhesive 

 disc, but Goto has expressed an opposite opinion. It is an important point in the 

 classification and could, no doubt, be quickly settled by watching the habits of 

 Olindias in the aquarium at Naples. 



Goto has investigated the development of the sense-organs of OUndioides formosa, 

 Goto, and has come to the conclusion that they are entirely derived from the ectoderm. 

 On the ground that the sense-organ is ectodermal, Goto transfers the Olindiidaa from 

 the TrachomedusaB to the Leptomedusre and places them under the Eucopidse. In 

 this Report I have left the Olindiidse in their old place for convenience sake, not that 

 I dispute Goto's account of the development of the sense-organs, but rather that I 

 am doubtful about their being true Leptomedusse. 



In 1901, when I was examining the medusae brought back from the Falkland 

 Islands by Mr. Rupert Vallentin (I regret that the report on the collection is still 

 unfinished, but hope to finish it next year), I cut some sections of the sense-organs of 

 Aglauropsis concmbii. The sense-organ lies in a corner, formed on one side by the 

 ectoderm containing nematocysts on the margin of the umbrella, and on the other 

 side by the endoderm of the circular canal. It is a globular vesicle containing an 

 otolith upon a short stalk. The wall of the vesicle is composed of a single layer 

 of cells which are in contact with the ectoderm, but isolated from the endoderm by 

 what looks like a layer of mesoglcea. As this layer took a definite shape and stained 

 a much deeper colour than the mesoglcea seen elsewhere, I, not knowing its origin, 

 was doubtful about its really being mesoglcea. I was puzzled for a time over the 

 sense-organ, not being sure whether the cells of the vesicle were ectoderm or 

 endoderm, but finally came to the conclusion that the deeply-stained layer between 

 the vesicle and the endoderm had some connection with the sense-organ and regarded 

 the whole sense-organ as endodermal. As the sections showed that the preservation 

 was not suitable for histological work (the specimens were preserved in formalin), I 

 did not attempt to trace the development of the sense-organ. 



After reading Goto's description of the development of the sense-organ of 

 OUndioides, I again examined the sections of Aglauropsis. I am now inclined 

 towards the view that the vesicle is ectodermal, and that it is cut off from the 

 endoderm by mesoglcea, but before coming to a definite conclusion I should like to see 

 earlier stages in development. 



Family : GERYONIID.E, Eschscholtz, 1829 ; ex Maas, 1893. 



Trachomedusae, with four or six radial canals, in the course of which are situated 

 leaf-shaped gonads. Blind centripetal canals. Stomach on a long peduncle. 

 Internal sensory vesicles. 



