64 



HYDROZOA. 



Fig. 14. 



Gemmation of Medusoids 



a, Dijplonema Islandica, showing 



young Medusoids budding from the tentacles ; b> Sarsiagemmifera, 

 ■with Medusoids arising from the sides of the polypite; c, Sarsia 

 prolifera, in which Medusoids are seen to sprout from the junc- 

 tion of the tentacles with the marginal canal. (All magnified.) 



L ucernariDj®. Still more singular phenomena 

 appear in the life-history of Lucernaridce. In 

 Aurelia, Cyanea, and Chrysaora, the ova originate 

 within the generative cavities of the gigantic repro- 

 ductive bodies previously described. Thence they 



unknown 



to the 



w.v w uiiOlUi i UUj JLAX OUlilC U.11XV11U V\JLl lilCtililCl^ W ^" v 



peculiar pouches formed aloug the margins of the 



yp 



Segment* 



to these pouches are, in all probability, fertilised by 

 contact with the diffused spermatozoa, 

 tion of the vitellus, and other primordial changes 

 are undergone by the young ovum while yet 

 within the pouch, from which, about the close of 

 the third day, it comes forth, to enj oy, for a brief 

 period, an active, free-swimming existence. At 

 first it appears as an oblong, flattened, ciliated 

 body, or < planula,' of verv minute size, composed 





