422 ZOOLOGY. 



Siphono2)1t07'a. 



Chuu (C). DasXorvensystemder Sipliouoplioren. Zool. Anz., 4. Jahrg., pp. IJr-lll. 

 Fewkes (J. W;xlt<'i). The Siphouopliores. II. The Anatomy and DevelopmCiit of 

 Agalma— contiunecl. Am. Naturalist, v. 15, pp. 186-195. 



Phanerocarpa^. 



Haeckel (E.). Oigauisation iintl Classificatiou der Acraspeden. Jma. Zeitschiift f. 



JSfaturw., V. 14, SuppJ.-Heft, pp. 20-29. 

 . Classification der Discomedusen. Jena. Zeitschrifl /. Nuiuno., v. 14, SiippJ.- 



Bcft, pp. 51-.'4. 



Medusw and Hydroid Folyps living in fresh water. 



Mention was made in the Smithsonian Eeport for 1880 of the occur- 

 rence of various medusiform acalephs in fresh water, and the change in 

 our ideas as to their adaptability for life in such a medium which the 

 facts entailed. "The tolerance by Medusae belonging to marine species 

 of fresh water under natural conditions was observed by Mr. Mosely, 

 at Browera Creek, in New South Wales" (Naturalist on the Challenger, 

 p. 272), and Mr. A. Agassiz communicated analogous instances ob- 

 served near Boston in a letter to Prof. E. Ray Lankester (Quart. Journ. 

 Micr. Sc, u. s., v. 20, pp. 483-485). Mr. George J. Eomanes has experi- 

 mented on Sarsia with reference to its tolerance of change, and recalled 

 that Prof. L. Agassiz made a partial experiment in 1850, and found that 

 a Sarsia transferred directly from salt water into a glass of fresh " will 

 at once drop like a ball to the bottom and remain forever motionless — 

 killed instantaneously by the mere difference of density of the two 

 media" (Mem. Am. Acad. Arts and Sc, 1850, p. 229). Mr. Eomanes, 

 however, found that while the Sarsia did really drop down as described, 

 instantaneous death did not ensue, hut if transferred back into salt 

 water within five or ten minutes the Sarsia would revive and regain full 

 vigor, but if allowed to remain in the fresh water as long as fifteen min- 

 utes recovery never ensued. Mr. Eomanes also sought to ascertain 

 whether the collapse of the Sarsia in fresh water was the result of a 

 difference of density, and his experiments, although not conclusive, ap- 

 peared to indicate that it was not, but rather, perhaps, due to the ab- 

 sence of the chemical constituents of its natural medium. It is to be 

 borne in mind that these exj)eriments were on the abrupt transfer from 

 the one medium to the other. As to the cases cited of the living of salt- 

 water species in fresh water, Mr. Eomanes "can only conclude from it 

 that a gradual transition from salt to comparatively fresh water, not 

 giving rise to such rapid osmosis" as takes jjlace in case of abrui)t 

 change, "is not so injurious to Medusse" as lie should have suspected. 

 He adds that "the whole subject is thus shown well worthy of further 

 experimental inquiry." (Quart. Journ. Micr. Sc, n. s., v. 21, pp. 162- 

 165; Phil. Trans. Eoyal Soc, v. 167, p. 744, etc) 



