Chap. IT. CLOSER AFFINITIES OF AURELIA. 



73 



the main cavity of the body, while, in a more advanced state, the interambnlacral 

 tubes communicate only indirectly with the digestive cavity, through the sexual 

 pouches. And among the Cryptocarpaj this affinity is towards the ^Eginida?, rather 

 than towards any other family, if we take into consideration that in the ephyra) 

 the radiating chymiferous channels are at first rather broad and flat, like the radi- 

 ating pouches of ^gina and Cunina, and become more tubular only at a later 

 period. Presently we shall have to consider more fully these affinities. The 

 second point of resemblance, between the ephyra? and the Cryptocarp*, lies in the 

 simpler structure and greater prominence of their eyes, which at first resemble a 

 speck upon a short tentacle, more than at any later period; and it is a fact, that, 

 in most Cryptocarpaj provided with eyes, these stand out from the base of the 

 tentacles. The comparatively large size of the veil is another striking feature 

 common to the ephyrJB and the Cryptocarpae ; and so prominent is this membrane 

 m the latter, that Gegenbaur has insisted upon its presence, as a distinctive character 

 of the Craspedota, to which all the Cryptocarpa? of Eschscholtz belong, from the 

 Acraspeda, to which he refers Aurolia, overlooking the existence of a veil in this 

 genus. The simplicity of the mouth in the ephyrfe is also a structural feature 

 characteristic of the adult Cryptocarpje, when compared to the extraordinary devel- 

 opment of the oral appendages in the adult Phanerocarpa\ It is, therefore, evident 

 that the young Aurelia has greater affinities with the naked-eyed Medusa?, in pro- 

 portion as it is nearer its earlier ephyra condition, and we shall soon see that it 

 loses, gradually, these affinities, as it assumes, gradually, more and more, the structural 

 peculiarities of its adult state. 



The difference already noticed between the ^ginidje and the other Cryptocarpa? 

 in the structure of their radiating chymiferous cavities, is of great importance with 

 reference to the natural affinities of this family. Gegenbaur, who first called attention 

 to their peculiarities, and separated them as a distinct family from the other 

 Craspedota, justly remarks that they have but a remote affinity to them. He 

 calls special attention to the pouch-like, radiating prolongations of the main cavity 

 and the mode of insertion of their tentacles above the margin of the disk, and 

 the sheath-like protection afforded their base by this peculiar relation. Now 'these 

 characters are entirely foreign to the type of the Cryptocarpc^ proper, in which 

 the tentacles are always marginal and in direct connection with the marginal 

 chymiferous tube, while the radiating channels are always simple tubes. On" the 

 contrary, we find that in the Discophora? proper, and especially in their lower 

 representatives, such as Pelagia and Nausithoe, the radiating channels are pouch- 

 like prolongations of the main cavity of the body, and the tentacles arise between 

 deep indentations of the margin of the disk, exactly as in the ^Eginida?. And 

 even in Aurelia, in which the tentacles seem to be marginal, a careful examination 

 VOL. IV. 20 



