338 ZOOLOGY. 



HYDEOZOA OR ACALEPHS. 



WATER IN MEDUSA. 



Some time ago it was stated by Professor Mobiiis that in a specimen 

 of Aurelia aurita, from the Bay of Kiel, it had been ascertained that 

 there was 99.82 per cent, of water, and consequently the solid matter 

 could only have formed a small fraction of 1 per cent. This statement 

 was so remarkable that, before acceptance, it required verification, and 

 Dr. Krukenberg has recently examined specimens of the class, with the 

 object of verifying or disproving the allegation.* 



Specimens of Aurelia found at Triest were examined, and it was found 

 that the water formed only from 95.84 to 95.79 per cent, of the total, 

 the solid existing in the ratio of from 4.21 to 4.66 per cent. Chrysaora 

 liyoscella afforded 95.75 per cent, to 96.3 per cent, of water, and there 

 was from 3.7 to 4.25 of solid substances. A large specimen of lih izostoma 

 Cuvieri was found to contain 95.392 per cent, of water, and consequently 

 nearly 5 of solid matter, of which there were 1.608 per cent, of organjp 

 and 3 per cent, of inorganic substances. It was concluded that proba- 

 bly the MedusiB generally exhibit a close approximation to these results, 

 and that in none is there so small a percentage of solid matter to be 

 found as in the case instanced by Mobius. 



EXTRA-MARINE MEDUSJE. 



There is, perhaps, no type of animals that has been generally regarded 

 as being so eminently characteristic of the open sea as the Medusie. While 

 representatives of the class exhibiting the hydriform condition have of 

 course been long well known as inhabitants of fresh waters, until recently 

 none of the medusiform groups have been specially noticed as having 

 been found elsewhere than in the sea. It has been said of them that 

 they dread nothing more than fresh water, and that such water is really 

 poison to them ; that even brackish water kills them immediately ; and, 

 further, that they need a water rich in oxygen and constantly renewed 

 by movements of the waves and currents. "The Medusw, in fact, have 

 almost an equal dread of fresh water, of stagnant sea-water, and of a 

 slightly too high temperature." Several cases, however, have been 

 recorded within the last two years which must materially modify the 

 accepted beliefs with regard to their habitat. 



FRESH-WATER MEDUSAE. ^ 



Mr. Agassiz has shownt that the idea respecting the exclusive con- 

 finement of Medusfe to perfectly salt and clean sea water is exaggerated. 

 He records that in an estuary back of Boston harbor, at West Boston 



* C. F. W. Krutenberg. On the distribution of the water of tbe organic and inor- 

 ganic compounds in tbe body of Invertebrates. Vcrgl.-Physiol. Stud. Kiisl. Adria. I, 

 part ii, pp. 7&-106. {J. E. M. S.\ 



t Agassiz (Alexander). Aa quoted in Joiirn. E. Micr. Soc, vol. iii, p. 968. 



