CtTNOCTANTHA. 51 



Cunoctantha and Cunina differ from each other only in the number of 

 tentacles, for while it had previously seemed that the presence of canals in 

 Cunina and their absence in Cunoctantha might be a good generic character, 

 the occurrence in the present collection of a typical Cunina without any trace 

 of canal system, and of a typical Cunoctantha with canals well developed, 

 proves that this view is untenable. More important, perhaps, than the dif- 

 ference in the number of metameres in these two genera, though previously 

 less emphasized, is the fact that in one, Cunoctantha, they are determinate 

 in number; in the other, variable in all species so far known. Solmissus differs 

 from both in the absence of otoporpae, — structures which occur in all species 

 of Cunoctantha and Cunina, at least in the primary generation. 



Cunoctantha Haeckel, 1879. 



Cunanthidae with only eight tentacles ; with otoporpae ; with or without 

 peripheral canal system. 



Maas (: 05) has shown that the several supposed forms which can be 

 grouped under this genus probably form not more than two distinct species. 

 These are C. octonaria McCrady ('57), including C. kollikeri F. Muller ('61 a ) and 

 C. incisa Mayer (: 00 b ) ; and C. discoidalis Keferstein and Ehlers ('61), synonyms 

 of the latter being C parasitica Metschnikoff ('81), and G. polygonia Haeckel 

 ('79). For the latter Maas has used Metschnikoff's name, C . parasitica, but from 

 an examination of the figures given by Keferstein and Ehlers ('61, taf. 14, 

 figs. 12-14), I am convinced that the specimens which they examined were 

 early stages of C. parasitica, from which they differ only in having but one 

 otocyst per lappet and very short gastric pockets, both of which characters 

 were observed by Metschnikoff ('81) in the development of the latter species, 

 so that it seems best to retain the older name C. discoidalis. 



Maas (: 05) has expressed some doubt as to whether Cunoctantha octonaria. 

 and C. discoidalis will finally prove to be distinct. The chief reason for their 

 separation, is the supposition that different methods of development occur in 

 the two forms, C. parasitica forming stolons, while the medusae of C. octonaria 

 develop directly, but F. Muller ( 61") observed stolons in the development of 

 C. kollikeri (certainly a synonym of C. octonaria), and Mayer (: 04) found a free 

 floating stolon of some species of this genus at Tortugas, Florida, where he 

 has also taken C. octonaria (incisa). Unfortunately Mayer was unable to raise 

 the medusae far enough for specific determination, but the stolon closely 

 resembled the one described by Muller. 



