224 CONTRIBUTIONS TO THE NATURAL HISTORY 



alcohol, or various saline solutions ; when the differences of shade introduced in the 

 tissues of different kinds has often proved a useful means of ascertaining structural details 

 otherwise indistinct, or altogether undiscovered. All these different modes of investiga- 

 tion have been repeatedly tried under various circumstances. 



I may be allowed to mention, also, that I have used, with great advantage, Goadby's 

 liquid for the preservation of Medusae, with all the care and precautions indicated by 

 Professor Edward Forbes, in his admirable Monograph of the British Naked-eyed Mediisce. 

 It is important that every one who repeats these investigations should be fully assured that 

 his success in preserving good specimens will depend altogether upon the care he takes 

 in using successively the liquids of different density, and also in changing regularly and 

 frequently the liquid in which the specimens are immersed, until they are fairly saturated 

 and the process of endosmosis has ceased to go on. I have lost most valuable specimens 

 from having trusted too soon to the preserving power of the liquid in its first appli- 

 cations. 



S ARS I A. 



In the year 1835, Sars published, under the name of Oceania tubulosa, a description, 

 with figures, of a small Medusa discovered by him on the shores of Norway. It is found 

 in that most remarkable little volume of his " Descriptions," * which contains the germs of 

 so many important developments in our knowledge of the lower animals. This species was 

 afterwards taken as the type of a new genus by Lesson, who, in his work on Acalephje,t 

 describes it under the name of Sarsia tubulosa. Since that time, a h\v species have 

 been added to those mentioned by Lesson. 



It would seem as if the genus Sarsia was now fairly established, as it rests upon 

 well-defined and easily ascertained characters ; but since it has been discovered that 

 Sarsia is only one condition of development of animals which differ widely at other 

 periods of the year, it now remains for us to ascertain under what generic name it 

 should finally stand in our system. For the common Coryna or Syncoryna represents 

 one of their stages of growth, and the Oceania or Sarsia is another. And it must have 

 been a high satisfaction to Sars, who first discovered the species, and introduced it to the 

 notice of naturalists, to have also been the first to perceive that these little Medusae 

 are developed from a polyp-like stem, which alternates in their generations with the 

 free Medusae. f 



* Beskriveher af Polypernes, ikc. Bergen, 1835. 4to. 



t Hisloire NaiureUe des Zoophytes. AcaUphes. Paris, 1843. 8vo. 



I Fauna Lilloralis Norvegicc. Christiania, 1846. fol. 



