ZOOLOGY. 339 



bridge (about one aiilo from the head of the harbor), and \ihere the 

 water, at the hist part of the tide, is ahiiost fresh and has a very sHght 

 salt taste, there is au abiuidauee of Hydroids, which "thrive remarka- 

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

 size." The species which have free medusce are Encope diaphana, E. 

 pi/ri/'onnis, and ObeJia commissumlis, and these are twice during -!4 hours 

 of the day exposed alternately to salt and nearly fresh water, and thrive 

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

 Other medusiie found near the same place, and which, at low tide, were 

 in fresli water, were species of Sarsiw, Fiaropsis, and Aurelia, and these 

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

 were found. 



NEW PALUDICOLOUS MEDUSA.* 



lu 1876, Dr. Dn Plessis discovered "in the middle of the discharg 

 ing canal of the salt-works of Villeroy, near Cette," a Medusa which 

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

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

 is a black putrid mud, stinking of sulphureted hydrogen," and the water 

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

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

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

 Hake of jelly, 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. The Medusa in question was ascertained to belong to the genus 

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

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

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

 the species in 1879, considers that it furnishes an example of the influ- 

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

 formation of one species into another, for he df)ubts not that the diminu- 

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

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

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

 oceanic form has been changed into violet, while the tentacles become 

 black. 



A FRESHWATER JELLY-FISH. t 



In the summer of 1880 Mr. Sowerby, the secretary of the 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 saliuarum, sp. n., uouvelle Meduse paludicole 

 dcs euvirons de Cette. Bull. Soc. Ta«(Z. ('2,) vol. xvi, pp. 39-45, pi. Also, Jh. Mikj. 

 Xat. Hist. (5), vol. iii, pp :«5-389. 



tLankester (E. Eay). On a uew Jelly-fisli, of the order Traclxomedusce, living in 

 fresh water. Nature, vol. xxii, pp. 147-148, June 17, 1880. See also vol. xxii, pp. 177-lbl, 

 (Laiikcster, AUmanu, Romanes); 218 (Allmann); 241 (Lankester) ; 290 (Allmann); 316 

 (Lankester). 



