30 ACALEPIIS IN GENERAL. Part I. 



a peculiar genus of Acalephs, and Ijoth as distinct IVoni all the other genera of 

 Polyps and Medusa^ known at that time. The genus Scyphistoma is considered 

 as intermediate between Hydra and Coryne ; Sci/plii-sloma Jillcoync, the only species 

 described, is characterized as having twenty-four to thirty-two tentacles, the mouth 

 as being retractile and protractile, and the ljod_y as annulate. This last indication 

 shows, tliat the tScjphistoma first observed by Sars was on the point of ])assing 

 to the Strobila condition. Tlie genus Strobila is thus descrilied : Animalia nunc 

 simplicia et lil^era, nunc plura invicem conjuncta, alterum scilicit super alterum 

 positum, ita ut seriem forment, cujus extremitas infima jjcdunculo brevi est affixa, 

 singulum animal disci formam referens, supra paidlulum convexum, sul>tus concavum, 

 margo disci in radios plures divisa. Os sul:>tus maxime prominens tetragonum. One 

 sj)ecies, Strohila odorudiafa : Margo disci in radios octo dichotomos divisa. When 

 free, these discs are said to move like small Medusa\ Tlie eight small ocelli lietween 

 the lobes of the eight rays were correctly ol)served, and com^iared to those of the 

 Medusa (Aurelia) ain-ita and Medusa (Cyanea) capillata. Thienemann, wlio furnished 

 the abstract for the Isis, suggests that 8ars should ascertain whether this is not the 

 embryonic state of some Medusa. >Sars himself considered 8tro1jila as estaljlishing 

 a transition Jjetween the fixed Zocipliytes and the Medusa-, while Ehrenljerg^ mis- 

 took it for a Lucernaria in the process of transverse division. 



In his later work, published in ISo-j, Sars gives a more detailed account of 

 the Strobila, and shows tliat tlie animal he had descril)ed as a distinct genus under 

 the name of Scyphistoma is simply an earlier stage in the development of the 

 Strobila, and that the free discs of the Strobila are tliemselves closelv allied to the 

 animals described by Eschscholtz as Ephyra, a genus referred )jy the latter to the 

 Acalepha? cryptocarpa\ This is illustrated l:)y figures, on his PI. 3d. These oljscrva- 

 tions establish beyond tlie possil)ility of a doubt the fact, that extraordinary changes 

 take place in animals that were at first considered to lie Polyps, and the growth of 

 which ends in the production of animals Ijelongiug unquestionably to the class of 

 Medusa'. In a later note, Sars declares" that he has satisfied liimself that the 

 Ephyi-a-like Medusa arising from his Stroltila is a younger state of the common 

 Medusa- (Aiu'elia) aurita, without, however, furnishing the evidence tif this assertion, 

 which is still questioned by Wiegmann." 



In 1841, Sars takes the whole matter up again, and in a masterly paper'' demon- 



^ EiiuKXCEKG (C. G.), Die Akaleiihen dcs ^ Wieginnnn's Arcliiv fur Naturgeschichtc, 1837, 



rotlien Meeres und der Organismus der ]Mrdu,<en vol. 2, ]i. 27G. 



der Ostsee, Berlin, 183G, p. 52. •> Saus (il.), Urbor die Entwickeluiig der Me- 



- Wiegmann's Arcliiv flir Naturgoscliielite, 1837, dusa aurita und der Cyanea eaiiillata, Wiegmann's 



vol. 1, p. 406. Archiv iiir Aaturgeseliichte, 18tl, vol. 1, p. 9-3t, 



