8 M. F. Muller on the Systematic Position of the Charybdeidse. 



cipated that this would derive support from the developmental 

 history. Still earlier, although information of the fact did not 

 penetrate to the place of my exile until subsequently, R. Leuckart, 

 following the same idea, had formed the section of Ceratostera, 

 but soon gave it up again; for his supposition has, as is well 

 known, proved to be quite destitute of foundation. Krohn saw 

 Pelagia noctiluca reproduce without change of brood, whilst 

 Busch traced the brood of Chrysaora, which is scarcely separable 

 generically from Pelagia, up to the polype-form. Among the 

 Hydroida, it has been shown by Gegenbaur that Trachynema 

 ciliatum, and by myself that Geryonia (Liriope) catharinensis, 

 are probably developed directly from the egg; whilst, on the 

 contrary, the supposition of the direct evolution of the JEginidcc, 

 founded solely upon the ciliary coat of the young of sEginopsis, 

 has lost its support by the discovery of ciliated brood in the 

 stomach of Cunina Kbllikeri. 



Nevertheless, my formerly imagined grouping of the Disco- 

 phorce. has become more and more plausible with every new in- 

 vestigation. It appears to me that in this case, as in so many 

 others, the unfettered intuition of the older observers has hit 

 the right course in uniting with Charybdea marsupialis andperi- 

 phylla the Charybdea bitentaculata, which is now usually placed, 

 under the name of JEginopsis mediterranea, J. Mull., or JE. bi- 

 tentaculata, Koll.*, in the family JEginida, at the end of 

 the Cryptocarpm. Not that I would support the union of Cha- 

 rybdea and ^Eginopsis in the same genus, or even, after the ex- 

 ample of Liitken, in the same family ; but I am of opinion that 

 the families Charybdeidse and iEginidse, Ggbr., are to be united 

 to form a group of the Hydromedusse equivalent to the Siphono- 

 phora, Hydroida, and Acalephse (in Leuckart's sense). To group 

 together the most highly organized of all known Hydromedusse, 

 and perhaps of all Ccelenterata, the Tamoya quadrumana, and 

 the ^Eginidte, which apparently represent the lowest step in the 

 series of Hydromedusse, and some of which, such as Eurystoma, 

 Koll., only digest by the cavity of the lower surface, which is 

 partially closed by the velum f, certainly long appeared to me to be 

 rather a doubtful course. Since I have been able to examine care- 

 fully a species extremely similar to this Eurystoma both in form 



* The difference of colouring can hardly be accepted as a specific di- 

 stinction in a group of animals in which, as in the Acalephse {Rhizostoma, 

 Chrysaora, &c.) and Hydroida (Corymorpha), the greatest variability of 

 coloration within the species may almost be regarded as the rule. 



t I did not think I might doubt this representation of Kolliker's (which 

 is probably erroneous) upon Gegenbaur's authority alone, as in other Me- 

 dusa I had not always found his statements perfectly well founded, — still 

 less on account of any il-priori notions respecting " a general plan of the 

 Medusas." 



