374 Proceedings of the Royal Physical Society, 
after extrusion, fully half an inch long, and have almost 
parted with the nutritive portion of the vitellus. There are 
many, however, that have made less progress, and have still 
a large yelk-mass attached to the upper part of the thorax 
immediately behind the pectoral fins. On the third day 
after exclusion from the ova, the mouth and jaws were quite 
distinct, the pectoral fins had appeared, and the outlines of 
the branchial arches were plainly visible. The cardiac con- 
tractile sac, which was seen in the embryo, was now found 
to contract and dilate sychronously with a fluid movement 
along the ventral aspect, which could be traced backwards 
four-fifths the length of the fish, where a notch in the deli- 
cate fin membrane appeared to indicate the separation be- 
tween the abdominal and caudal portions of the animal. 
The progress of development has been watched daily, and 
will be more fully detailed when the observations are com- 
pleted. 
As it is uncertain whether the young fry will exist long 
enough to pass into their adult condition, I have thought it 
proper to give this brief notice to the Koyal Physical So- 
ciety, and at the same time to exhibit living specimens, 
along with pencil drawings illustrating the various phases 
of development from the first rotation of the embryo seen 
in the ovum until the present time. 
Dr T. S, Wright mentioned that he had noticed a similar 
development, but was doubtful if the ova were herring 
spawn. 
III. (1.) On the Difference between the young Herring, Clupea harengus, 
cmd e/i-e )%)m#, Clupea sprattus. (2.) On the Food of Fishes. By 
J. M. Mitchell, Esq. 
Mr Mitchell described the various differences between 
these distinct fishes ; and proceeded to detail the results of 
the examination of the contents of the stomach in various 
genera and species of fishes. 
IV. On Phryxus Paguri. By John Anderson, M.D. 
In the month of May last year, when dredging in the 
Firth of Forth, I had the good fortune to meet with this in- 
