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PROCEEDINGS OF THE 



[Dec, 1857. 



constriction p. As will be seen from the figures, the lobe e 

 was greater than the double lobe d, and in neither of them 

 could I make out any indication of the formation of internal 

 organs. But it is possible that such were in course of for- 

 mation, for I was unwilling to use any means for reducing the 

 organism to quiescence, which might have resulted in their death 

 since, with ciliary blades and tentacula of the type of young 

 Bolinas,they were yet very far from the Ctenophorous form, and I 

 wished, if possible, to trace their further changes. All of these de- 

 scribed occurred within the space of three hours about midnight, 

 and the next morning these interesting specimens were dead. 

 While under examination, their great restlessness and transpa- 

 rency rendered it impossible to make out any thing with certainty, 

 in regard to their internal structure. The only appearance which 

 seemed to have connection with this, was the appearance of a 

 cavity immediately under the ciliary arc, (ff. 8, 11 and 12(?) s.) 

 This, perhaps, was a portion of the ambulacrai tube of the original 

 animal. 



Since these observations were made, however, I have frequently 

 found small asymmetrical Bolinas, usually with one side tolerably 

 well developed, while the other had its parts just sketched out. 

 These would gradually develope themselves in my jars to perfect 

 symmetrical Bolinas. And 1 think that they, likewise, are indi- 

 viduals developed from previously existing Bolinas by fission, 

 and that they constitute a stage subsequent to those figured PI. 14. 



From the observations hitherto made it appears that the devel. 

 opment of the Ctenophorous medusae is an homogony, and that the 

 embryo early assumes the form of the youngest stages of hydroid 

 larvae, passing directly from this into the form of a Ctenophore 

 Does this embryological history then skip over the types of Hydroid 

 and Discophorous Medusae? Certainly, to all appearance, the 

 campanulate, or umbrella, or watch-glass shape of these lower 

 medusae is never presented, and the homology of parts has been 

 so difficult to trace between the two groups of Ctenophora and 

 Discophora, that a very able European Naturalist, Vogt, was led to 

 consider them altogether distinct, and removed the Ctenophora to 

 the under-kingdom of Mollusea. It appears to me, however, that 

 the embryology of these medusae confirms a suspicion which I 

 had before entertained of their homologies, viz: that they hold to 

 the Discophores a relation as to homology, very similar to that 

 which Echini proper and Holothuridae hold to Star-Fishes. This 



