156 
SECOND WINTER MEETING. 
The second Winter Meeting of the Club was held at the 
Lecture Theatre of the Science Schools, in Gloucester, on the 
afternoon of Tuesday, 17th February, when papers were read 
by Dr. Day on the “ Burbot and Air-bladders of Fishes ;” and 
by Dr. Wricut F.B.S., on “The Modern Classification of 
Ammonites.” 
Dr. Day stated that the Burbot is a fresh-water fish, which 
is found throughout northern and central Europe, also in 
Canada and the adjacent portions of the United States, while 
in Great Britain it is restricted to Durham in the north, 
extending along the eastern and midland counties as far south 
as Cambridgeshire and Norfolk; while the belief is that its 
numbers are decreasing, and that the species is doomed to 
extinction at no very distant date. This fish possessing an air- 
bladder of the Physoclistic, or entirely closed form, and having 
no ossicles by which it is connected with the internal ear, leads 
one to examine into what is the air-bladder in fishes ? and what 
are its functions ? 
In the embryo this organ is perceived originating as a bud 
or offshoot from the upper portion of the alimentary canal, or 
even from the stomach; this offshoot elongates into a blind tube, 
and then enlarges at its terminal extremity into what will 
eventually form the air-bladder; consequently at some time of 
a fish’s life there exists an open tube connecting its air-bladder 
with the alimentary canal, into which latter it opens, usually 
on the upper, rarely on the lateral, and occasionally on the 
inferior wall. 
Dr. Day traced the varied adaptations of the air-bladder in 
the Dipnoids or highest class of fishes, and the communication 
during life, by means of a duct and glottis, with the cesophagus. 
He spoke of the ducts in Lepidosiren, Protopterus and Ceratodus 
as homologous with the windpipe, while the functions of the 
air-bladder are analagous to those of lungs. 
The Ganoids afford instances very similar to those which 
obtain amongst Dipnoids. That the air-bladder is homologous 
