ZOOLOGY. 339 



bridge (about one mile from the bead of tbe barbor), and "\;\'bere tbe 

 water, at tbe last part of tbe tide, is almost fresb and bas a very sligbt 

 salt taste, tbere is an abundance of Hydroids, wbicb "tbrive remarka- 

 bly well on tbe drainage of the district, and grow to an unusually large 

 size." The species which have free medusiE are Eucope diaphana, E. 

 pyriformis, and Obelia cormmssnralis, and these are twice during 24 hours 

 of the day exposed alternately to salt and nearly fresb water, and tbrive 

 under the change, both in their hydriform and medusiform conditions. 

 Other medusfe found near tbe same place, and which, at low tide, were 

 in fresb water, were species of Sarsice, Piaropsis, and Aurelia, and these 

 seemed unaffected by the large quantity of fresh water in which they 

 were found. 



NEW PALUDICOLOUS MEDUSA.* 



In 187G, Dr. Du Plessis discovered "in the middle of the discbarg 

 iug canal of tbe salt-works of Villeroy, near Cette," a Medusa which 

 inhabits in the summer the stream thereof and tbe near-lying waters. 

 The canal is about two or three yards broad and one deep. "The soil 

 is a black putrid mud , stinking of sulpbureted hydrogen," and tbe M'ater 

 is perfectly stagnant, very brackish, and exposed all day long to tbe full 

 rays of tbe sun. "The Medusa always inhabits the lower surface of 

 islets of floating algae. On removing these it is seen clinging like a 

 flake of jell3% shining like crystal." They only occur in June and July, 

 and were looked for in vain in spring as well as in September and Octo- 

 ber. Tbe Medusa in question was ascertained to belong to the genus. 

 Cosmctira, a representative of the family of Oceanidie, and is very 

 closely related to, though much smaller than, tbe Cosmetira punctata, 

 which is abundant in the contiguous sea. Dr. Du Plessis, who described 

 tbe species in 1870, considers that it furnishes an exami)le of tbe influ- 

 ence of tbe surrounding medium in the gradual modification and trans- 

 formation of one species into another, for be doubts not that tbe diminu- 

 tive Cosmetira is a decendant of the Cosmetira punctata, from which it 

 has become modified and reduced greatly in size, while tbe canals and 

 stomach have assumed a green color, and the general rose-color of tbe 

 oceanic forai bas been changed into violet, while the tentacles become 

 black. 



A FRESHWATER JELLY-FISH. t 



In the summer of 1880 Mr. Sowerby, tbe secretary of tbe Eoyal Bo- 

 tanical Society of London, noticed quite a number of small animals, 

 which were soon ascertained to be medusae, in a warm-water tank in 



* Du Plessis, G. Etude sur la Cosmetira salinarum, sp. u., nouvelle Mtiduse paludicole 

 des environs de Cette. Bull. Soc. Vuud. (2,) vol. xvi, pp. 39-45, pi. Also, An. Mag. 

 Kat. Hist. (5), vol. iii, pp :}d5-389. 



tLaukester (E. Eay). On a new Jelly-fisli, of the order Trachomcdusce, living in 

 fresh water. Natin-c, vol. xxii, pp. 147-148, June 17, 1880. See also vol. xxii, p^i. 177-181, 

 (Lankcster, Allmann, Romanes); 218 (Allmann); 241 (Lankester) ; 290 (Allmann) ; 316 

 (Lankester). 



