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 Eoyal 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, 

 and the Sprat, 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- 



