2544 Fishes. 



the more internal part, until at last it makes its escape from its prison. The above 

 description, the author stated, may be considered as a brief summary of the changes 

 which take place within the eggs of fishes generally after impregnation in the natural 

 manner, and he afterwards proceeded to describe the general appearance of the 

 embryo of the Trout soon after its exclusion from the egg, the ovum from which it 

 was obtained having been artificially impregnated, according to a plan first adopted 

 by Mr. Gotlieb Boccius, and ably carried out by him, a full description of which is 

 given in the 'Zoologist' (Zool. 2193). 



The author then mentioned that he was indebted to the liberality of Samuel 

 Gurney, Esq., Jun., for the specimens from which he was enabled to draw up the 

 following communication. 



The first specimen which was received, and the one which furnished the greater 

 part of the subjects of the paper, was two days old, about three quarters of an inch in 

 length, and consisted of an elongated portion or body, to the lowest edge of which was 

 attached a more or less oval vesicle termed vitellicle. 



The body was thin and transparent, of a yellowish colour, with occasional dark 

 spots of pigment, scattered principally about the dorsal region, and having in its 

 centre a lighter part, which marked out the line of the vertebral column. It was 

 provided with fins of great delicacy, of which the caudal, dorsal, and pectoral were 

 most developed, but as yet had not attained their proper shape, the caudal being at 

 its free edge, not much broader than the part of the body to which it was attached ; 

 the pectorals on the contrary were of the normal shape, and always in a rapid state of 

 movement. 



The head was short and broad, and the mouth terminating in a point, was placed 

 in an inferior position. The eyes were very large in proportion to the size of the head, 

 of a black colour, the iris covered with a silvery membrane, and having a large 

 circular pupillary aperture. 



The body tapered gradually from the head towards the tail, but was not con- 

 stricted before the giving off the tail, as seen in all other fish. 



The vitellicle was connected with the lower or abdominal surface of the body, and 

 was of a yellowish colour, with one or more globules of darker yellow, situated in some 

 portion near its .point of attachment ; it was supplied with large blood vessels, visible 

 to the naked eye, especially on the left side, where a large vein is situated, which 

 made a striking difference in the appearance of the two sides of the fish. 



All the principal blood-vessels were visible to the naked eye, and even the heart, 

 which was rapidly pulsating, immediately in front of the vitellicle. 



When one of these little creatures was examined with a power of forty linear, the 

 whole scheme of the circulation could be observed, and as the author stated, was the 

 most wonderful of all the phenomena exhibited by the microscope : he thought proper 

 first to devote attention to it. 



At this early stage the heart, situated immediately in front of the vitellicle, and in 

 that part which might be called the neck, was found to consist of two parts or cavities, 

 one large and flabby, the auricle, the other smaller and more compact, the ventricle ; 

 arising from this last, was seen a straight vessel which passed towards the head, and 

 divided into a number of small branches, each one going to a rudimentary branchial 

 aich and bending back, united to form a single vessel, the aorta, which ran in a 

 straight course, below the vertebral column towards the tail, where it expanded into 

 two principal branches, which were further subdivided and supplied one side of each 



