272 Mr D. Ellis on the Natural History of the Salmon. 



Description of Plate III. exhibiting the Evolution of the Ova 



of Salmon. 



Fig. 1. The ovum of the natural size, after the embryo has become 

 quick in it : at this stage, the body of the embryo has a 

 pinkish tinge, and the eyes are disproportionably large. 



Fig. 2. The shell just burst, and the head of the embryo protruding. 



Fig. 3. State of the subject eight hours after it had burst the shell, at 

 which time the pulsations of the heart are very visible. 



Fig. 4. The shell just thrown oflf, with the tail drooping : before the 

 shell bursts, the tail envelopes the yolk or bladder, which is 

 seen attached to the body of the fish. The shell itself is 

 transparent, and about one-third part of it is fractured by 

 the fish in extricating itself. 



Fig. 5. The tail of the young fish has now become straight ; the mouth 

 is distinct, and the lower jaw and pectoral fins, which are 

 quite transparent, are in motion, and keep time with the 

 heart, which beats from 60 to 65 times in a minute : At 

 first, the body of the fish is colourless, with slight marks of 

 articulation of the bones, or of stripes on the skin ; the bag 

 attached to the fish is transparent, and is filled with a light 

 # amber-coloured albuminous fluid, with some drops of a clear 



rose-coloured oil in it. 



Fig. 6. Represents fig. 3. magnified. The bag beneath the belly is ex- 

 tremely soft and yielding, and the shell is still seen bind- 

 ing the young animal. 



Fig. 7. Represents fig. 5. magnified. The heart is placed before the 

 pectoral fins, and under the throat, and is connected with a 

 large bloodvessel that runs along the front and bottom of 

 the bag, as is more clearly seen in fig. 8. The bag, which 

 was at first round, becomes, in a day or two after the fish 

 leaves the shell, more and more elongated ; with a micro- 

 scope, the circulation may be seen. The blood flows from 

 under the body of the fish, through vessels which ramify 

 upon the sides of the bag, and from these it is collected, 

 and continued into the large vessel before mentioned, which 

 is connected with the heart : from the heart the blood is 

 again thrown, with regular pulsations, into the vessels of 

 the head and throat, where it is seen to assume a darker hue, 

 as well as to the other parts of the body : air, it is said, or 

 some transpaient fluid, is seen to circulate, in equal quan- 



