54 ACALETIIS IN GENERAL. Part I. 



tube, ami even the inverted vhn of the margin of tlie bell so constant in naked-eyed 



Mednsaj ( i^^y. 30) ; and though no mouth is descrilx'd, I can hardly suppose that it is 



wanting. The radiating tubes imply the circulation of a tluid, 



and tliat fluid is in all naked-eyed Medusre derived from the 



surrounding medium, and introduced either through a proboscis 



or through a cruciate opening in the centre leading into the 



radiating tubes. The foet that in Staurophora^ I have found 



an immense mouth where none was suspected, leads me to 



D.rnYEs'''stEBOLD.i, K.,11. .^upposc that tlus youug Diphyes and the so-called swimming- 



{Cqned from Gegenbaua:) bclls of tlic Siphonoplionu generally, uiust luivc sucli au Oral 



-a swimmiDg-beii developed opeuuig, Avlucli has probahlv not been remarked only Ijecause 



from the embryonal body. , . iiii^*i 



such an openuig would not ijc looked tor \\\ what was sup- 

 posed to Ijc a niere organ. Yet, considering the strict homology between the 

 open Polyps, so called, and the closed sacs mixed with them in Physalia, and like 

 them provided with tentacles, it may Iw that the swinuning-lxdls are not open 

 externally, and only connnunicate with the main axis. 



Be this as it may, the swimming-bells of the Diphyidte cannot be coinpared 

 to the swimming-bag of the Phj-salia, which, as we have seen, is the common 

 base of all the Ilydroids of that connnunity ; nor is it homologous to the so- 

 called swimming apparatus of the Physophoridtw The only part in these different 

 communities really identical in all Siphonophora^ is the canal marked e in Fifjs. 34 

 and 35, along which hang the heterogeneous individuals of the community in Diphyi- 

 da^, Physophorid*, and Physalida? ; in the same manner as the many individuals of 

 the connnon Hydroids are attached to their hollow axis. In Diphyes proper there 

 exist, generally, two so-called swimming-bells of nearly the same size, though occa- 

 sionally but one is obser-sed, and in others the lower one a2)pears sometimes so 

 much smaller than the upper one, that, taking these facts in connection with the 

 facts observed by Gegenbauer respecting the origin of the first swimming-ljcU from 

 an egg, it is natural to infer that the second swimnung-bcU arises from the main 

 tube of the first, and gradually enlarges to the same size ; in the same manner 

 as in the proliferous naked-eyed Medusae {Figs. 12, 13, and 14), in which one of the 

 four radiating tubes becomes the liasis of attachment of numerous lateral Ijclls. It 

 is fiirther to be observed, that tla' pendent string of Dii)hyes, with its numerous 

 individuals, is only a continuation of that same tulie which connects the two swim- 

 ming-bells, and that the individuals attached to it arise also as buds from it. But 

 here we perceive a variety of parts which require our special attention. 



The individuals described as Polyps, or suckers, in Diphyes, are as it were 



1 Agassiz (L.), Cuiitributions to tlic Natural History of the Acaleplis, Part. I. p. 300. 



