1893.] Zoology. 571 
ZOOLOGY. 
A Medusa from Lake Tanganyika.—In the “Annals of 
Natural History,” for the present month, will be found an account of 
a very interesting zoological novelty. Mr. R. T. Giinther describes 
and figures a remarkable new form of Medusa, or jelly-fish, that occurs 
in Lake Tanganyika. Until recent years, when the little Limnoco- 
dium was found living in the Victoria lily-tank of the Botanic Gar- 
dens, Regents Park, it was believed that the Medusæ were nearly 
exclusively oceanic. It is now shown that the freshwater lake Tanga- 
nyika is the home of a peculiar member of this group. The existence 
of such an organism in Tanganyika was asserted some years ago by the 
German naturalist, Dr. Boehm, and Professor v. Martens, of Berlin, 
even went so far as to name it Tanganjice, although he had never seen 
a specimen. Mr. Giinther now supplies us with a full description of 
this singular Hydrozoon, which he refers to a new genus, Limnocnida, 
adopting the suggestion of v. Martens as to its specific name. Lim- 
nocnida tanganjice is, as might have been anticipated, perfectly differ- 
ent from all the members of the group hitherto known, and probably 
represents a distinct family, but its exact position cannot be settled 
positively until the mode of its development has been ascertained. 
(Nature, April 13, 1893.) 
The Air-Bladder and Weberian Ossicles in the Siluroid 
Fishes.—A study of the physiology of the Weberian ossicles and of 
the air-bladder in general has been made by Professors T. W. Bridge 
and A. C. Haddon, for the purpose of discovering the physiological 
relation of the Weberian mechanism to one of the several functions 
that have been ascribed to the auditory organ or to the air-bladder. 
With this object in view they discuss (I) how far the function of the 
Weberian mechanism is conditioned by the anatomical structure of 
_ the air-bladder and auditory organs as well as by the character of the 
mechanism itself; (II) to which of the known functions of the air- 
bladder and auditory organ the Weberian ossicles are to be regarded. 
as accessory structures; and (IIT) the utility of the mechanism to the 
fish possessing it. 
The alee find (I) that from the anatomical structure of the parts 
the Weberian apparatus is better adapted to register the more forcible 
distentions or contractions of the anterior chamber of the air-bladder 
