M. F. Miiller on the Systematic Position of the Charybdeidas. 9 



and in the development of the brood budding in the stomach, and 

 since I have again obtained Eschscholtz's admirable f System der 

 Akalephen/ this hesitation has disappeared ; and I now regard 

 my view as sufficiently well founded to venture to submit it to 

 the judgment of zoologists. 



The incompatibility of the Charybdeidce with the Acalephas 

 of Leuckart has already been spoken of. Cunina, JEginopsis, 

 and their allies stand in a precisely similar position towards the 

 other Cryptocarpas or Hydroid Medusas. The disk of the latter, 

 although very variable in form, is still always entire at the mar- 

 gin, and either smooth, as in the other Acalephs, or furnished 

 with slightly projecting ridges running from the middle of the 

 back ; they have always radiating vessels and an annular canal, 

 and the former, except when very numerous, in a fixed number; 

 the marginal vesicles, when present, are always roundish and 

 sessile ; the marginal filaments, although very variable in struc- 

 ture, always occupy the immediate vicinity of the annular vessel. 

 Lastly, in the structure of the sexual organs, the Hydroid 

 Medusas approach the Acalephas (Leuckt.) or Phanerocarpse ; 

 for, although their forms are exceedingly numerous, the extremes 

 are united by a tolerably close series of intermediate forms (from 

 the astomatous sexual clubs of the Medusas of Corymorpha to 

 the densely appressed ramifications along the radiating vessels 

 of Olindias*), they still always occupy the external wall of the 

 gastrovascular system, and empty their products externally. On 

 the other hand, the disk of Cunina and its allies is frequently, if 

 not always, notched at the marginf, and, as in the Charybdeidce, 



* Olindias, nov. gen. Habitus of Thaumantias mediterranea, Ggb. ; 

 four radiating vessels, and numerous (more than 100) retrograde vessels ; 

 at the margin extremely extensible filaments and slightly moveable tenta- 

 cles, both hollow and of indefinite number ; at the base of the tentacles are 

 the marginal vesicles in pairs ; the sexual organs are arborescently ramified 

 along the radiating vessels. It is probable that the filaments (Fanyfaden) 

 on the radiating vessels of Melicertum are nothing but sexual organs, and 

 this the rather, as even in the structure of the marginal filaments Olindias 

 approaches most closely to Melicertum. As a transitional structure from 

 the stomachal to the peripheral sexual organs, I may cite, not to refer to 

 undescribed forms, Lizzia Kollikeri, in which, according to Gegenbaur's 

 observation, confirmed by me on a nearly allied species, the sexual gland 

 lying on the stomach is traversed by a branch of the radiating vessel. 



t Gegenbaur is of opinion that the possession of a velum presupposes 

 an entire margin of the body, and for this reason, apparently, he denies, 

 in opposition to Eschscholtz and Kblliker and in contradiction to himself, 

 the notching of the margin in the JEyinida; for in JEgineta Jlavescens he 

 shows the gelatinous substance continuing itself in considerable thickness 

 upon the stomachal sacs ; in the intervals, therefore, there are gaps or 

 notches of the gelatinous substance, i. e. " the body," over which only 

 membrane is stretched; as in the JEginida, which are destitute of an 

 annular vessel, only the cessation of the gelatinous substance can indicate 



