1905.] THE MEMBRANOUS LABYRINTH OF CERTAIN ANIMALS. 143 



Marcli 7, 1905. 



Dr. ^y. T. Blanford, C.I.E., F.R.S., Vice-President, 

 in the Chair. 



Dr. Albert A. Gray, introduced by Mr. Macleod Yearsley, F.Z.S., 

 exhibited a series of lantern-slides made from photographs of the 

 Membranous Labyrinth of some animals, and made the following 

 remarks : — 



While the labyrinth of the fishes has been investigated by many 

 observers and with very satisfactory results, the structure as it 

 appears in reptiles, amphibians, bu-ds, and mammals has not been 

 so exhaustively treated. This is due to the difficulties of preparing 

 the organ. These difficulties recently have been to a certain extent 

 removed ; and I propose to describe as briefly as possible some of 

 the features wdiich have been discovered. 



In Man there is found in many individuals an accessory ampulla, 

 as I propose to term it, at the posterior end of the horizontal 

 canal, in addition to the normal one at the anterior extremity. 

 This ampulla does not seem to have any special physiological 

 significance, since it is not supplied by a nerve, and moreover is not 

 found in all individuals but only in four out of six. I have not 

 found it in any of the lower animals except the Sturgeon, but it is 

 quite probable that with more material at hand it will be found 

 in some other animals. 



The labyrinth of the Seal is remarkable on account of its size, 

 the irregular shape of the semicircular canals, and most of all on 

 account of the presence of otoliths of considerable dimensions. 



It may be that this development of the otoliths in the Seal has 

 some relationship to the life of the animal in the water, as it is 

 well known that in the fish the otoliths reach a size far greater 

 than they do in any other animal. On the other hand, it may be 

 that the development of the otoliths, and indeed of the labyrinth 

 as a whole, is connected in some way with the migratory habit of 



the Seal. 



The perilymphatic spaces of the semicircular canals of the Seal 

 are, like those of Man, of considerable size, and difier in this 

 respect from those of the Cat and the Rabbit, 



The Cat has a labyrinth typical in one respect of a large 

 number of mammals ; "that is, in the almost com]Dlete absence of a 

 definite perilymphatic space in the semicircular canals. Indeed, 

 this space is not visible except at the corners where the ampullse 

 of the canals debouch from the canals themselves. The cochlea 

 of the Cat is part of a cone sharper than that of many mammals, 

 but not quite so sharp as that of the Guinea-pig. 



The Rabbit has a labyrinth similar to that of the Cat, but the 

 cochlea is blunter in appearance. As in the Cat, there is no 

 perilymphatic space in the canals. The ligamentum spirale is 

 not so well developed as in many other mammals. 



In addition to the already well-known features of the labyrinth 

 Peoc. Zool. Soc— 1905, Vol. I. No. X. 10 



