﻿Dec, 1856.] 



ELLIOTT SOCIETY. 



55 



Description of Oceania (Turrit op sis) nutricula nov. spec, and the 

 embryological history of a singular Medusan Larva, found in the 

 Cavity of its Bell. — By John McCrady. 



In the year 1851, Prof. Joh. Miiller described a remarkable 

 Acaleph and its embryology as observed by him at Marseilles and 

 Nice. Vide Miiller' s Arch. 1857, p. 272, plate xi. This animal 

 had a hemi-spherical disk whose margin was scalloped, and from 

 the upper part of which proceeded two long and peculiar tentacula. 

 The development of this species to which Miiller gave the name 

 JEginopsis mediterranea. was evidently a direct metamorphosis, 

 being unlike that of other Medusas, not subjected to alternation of 

 generation. At a later date (1852) the same Medusa was observed 

 by Kolliker, at Messina, and in addition to the details given by 

 Miiller, he was enabled to state that the digestive cavity terminated 

 in a simple oral Gpening, and was connected with eight lobes in 

 which he found ova or spermatozoa, according to the sex of the 

 individual. None of the specimens, examined by Miiller, had 

 probably arrived at maturity, Kolliker having observed a differ- 

 ence of form between the perfect individuals, and those which had 

 i not yet acquired sexual organs, which tended to identify the latter 

 with the last stage observed by Miiller. He also found on the mar- 

 gin of the disk, at the middle of each lobe, an otolithic vesicle 

 (Gehororgan.) Gegenbaur, in Zeitschrift f. Wissen. Zool. 1S56, 

 in a valuable paper on the Medusae, confirms the observations of 

 Miiller and Kolliker, having observed repeatedly, at Messina 

 (1852-53,) the embryology of this species which he characterises 

 as an Homogone, a direct metamorphosis without the intervention 

 of alternate generation. He also places the animal in his family 

 of iEginidae, whose principal characteristic is a large and broad 

 digestive cavity from the margins of which proceed pouches cor- 

 responding to the number of lobes of the scaiioped disk margin. 

 These pouches appear to contain the sexuai products when pre- 

 sent, but it is to be observed that these have not been observed for 

 the greater part of the species. The presence of otolithic capsules 

 (Randkorper.) and the peculiar position of the tentacula are like- 

 wise characteristic of this family. 



In 1853, at Messina also was found by Kolliker a Medusa, 

 Eurystoma rubiginosum, in the disk cavity of which were found 

 larvae. These developed themselves afterwards into a form of 

 Medusa which he named Stenogaster comp/anatus, and which also 

 evidently, from his description, refers itself to the iEginidae. 



