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PROCEEDINGS OF THE 



[Bee., I856v 



that of &ginopsis mediterranea as observed by Miiller, and con- 

 firmed by Koliiker and Gegenbaur, we see that in all essential res- 

 pects they are the same. Though the ciliated embryo of JEginop- 

 sis mediterranea swims freely in the sea, and accomplishes its 

 metamorphosis without shelter or protection from the parent, while 

 that of Turritopsis remains within the bell of the mother and feed- 

 ing from her mouth, until it is ready to begin its Medusa-life, yet 

 this is a difference analogous only to that between the ciliated 

 planule of Companularia, and the locomotive hydra of Tubularia. 

 One important distinction, however, is to be noted, — the earliest 

 hydra form of each is bi-tentaculate, but the larva of iBginopsis 

 preserves this bi-tentaculate form through life apparently, while 

 that of Turritopsis exchanges it early for a multi-tentaculate fornu 

 This is consonant with the inferior type of iEginopsis, which, ac- 

 cording to Koliiker, attains sexual maturity, under a form which 

 would refer it, as both Miiller and Gegenbaur have actually done, 

 to the group of iEginidae, while Turritopsis belongs to that of Oce- 

 anidae. The ultimate stage of iEginopsis is analogous to the last 

 which I have traced in the history of the Turritopsis embryo. 



The embryology of Stenogaster complanatus in the disk cavity 

 of Eurystoma rubiginosum is also identical with that of the larva 

 I have described, with the exception that there the tentacula ap- 

 pear to be developed one by one, instead of appearing in pairs. 

 No sexual organs have been observed, either in Stenogaster or the 

 similar form I have described. 



This singular family of iEginidse, to which perhaps should be 

 referred Polyxenia cyanostyla (Kschscholtz) contains at least 

 very few forms in which sexual organs have been recognized. 

 While it is extremely probable from the considerable size of many 

 of the species, that they reach maturity under the iEginoid form, 

 yet it appears more probable that the smaller species, even though 

 possessing spermatozoa and ova, may be the larvae of higher Me- 

 dusae. It may perhaps be found that JEginopsis mediterranea is a 

 larval Saphenia. On the other hand, it is true that I have not ob- 

 served the actual metamorphosis of the larva described in the pre- 

 ceding pages, into the form of Turritopsis. But the fact that when 

 larvae are present in the bell of the presumed parent her ovaries 

 are either entirely empty of ova, or nearly so, seems to me to ren- 

 der it scarcely doubtful that these larvae are truly the young of 

 Turritopsis, and must eventually, either directly or through the 

 medium of gemmation reach the form of Oceanidae. 



