8462 



Fishes. 



at the part corresponding to the back of the fish ; you will then see a tiny head with 

 black eyes and a long tail pop out, and the new-born creature gives several convulsive 

 shudders in his attempts to quit himself from the now useless egg-shell. Poor little 

 fellow ! he can't manage to get out — the shell is too tight for him. I take, therefore, 

 a soft hair-pencil, press lightly on the egg-shell: he seems to know I am his friend; he 

 gives another vigorous kick or two, and is free : he has commenced life. If we judge 

 from his motions he must enjoy life, for away he swims as fast as his tiny fins and 

 wriggling tail will carry him round and round in a circle, and then plump down he 

 goes to the bottom of the tank and reclines upon his side, breathing with his gills for 

 the first time in his life. As to food, Nature has kindly packed up all the nourishment 

 that it will want for some six or eight weeks, in a neat little bag or parcel which she has 

 affixed to the body of the fish, in such a manner that it shall be gradually absorbed into 

 the general system. This bag or umbilical vesicle is much too heavy for them, and 

 soon brings them to the bottom, like a bullet at the end of a fishing-line. So far so 

 good ; but cannot we see and learn more about the young fish ? Get out the micro- 

 scope, and place a young new-born salmon under a low power, and you shall see one 

 of the most beautiful sights ever beheld by human eye. You shall see the tiny heart, 

 which is situate just underneath the lower jaw, going pit-a-pat, pit-a-pat; you shall 

 see the blood at one instant in one cavity of the heart (where it appears like a red 

 speck) ; at the next instant it is in the other side of the heart: and so it goes on, day 

 and night, never ceasing, never tired — a great forcing-pump, propelling the hlood to 

 all parts of the body, and gradually building up the frame of a future king of fishes. 

 I counted the pulse of the salmon when it was under the glass, and ascertained that 

 it averaged about sixty in the minute. Just below the heart can be seen on the um- 

 bilical vesicle (when the fish is in the water) a bright red streak. Examine this under 

 the microscope, and you will see that this red streak is in fact a main artery ; with a 

 high power you can see plainly the minute blood-disks coursing along between the 

 walls of this elastic tube. The minor red streaks upon the umbilical vesicle can in 

 the same way be made out also to be blood-vessels, containing blood-disks running 

 along at a great pace. Again, down the centre of the transparent body of the fish can 

 be seen, with the unassisted eye, two tiny streaks ; the microscope shows that these 

 also are blood-vessels, and that the blood in the one is running towards the head, in 

 the other towards the tail. A more complete and beautiful demonstration of the circu- 

 lation of the blood never was yet placed under a microscope. The eye is in perfect 

 working order at the moment of birth, though the rest of the body is far from 

 perfection. It is most curious to observe the effect of temperature on the development 

 of the ova. Those at the ' Field ' office began to hatch out some five or six days before 

 those in the Zoological Gardens. The reason is obvious : the temperature of the 

 water running over the eggs at the ' Field ' office is 52°, at the Zoological Gardens in 

 the open air it is 43° only, and these fellows have not as yet begun to open their egg- 

 cases. Those, however, which I placed in the aquarium house at the Zoological are 

 hatching out fast." 



Salmon Ova not the Food of the Water Ouzel.. — The notice in your paper of last 

 Saturday (the ' Field ') that one of these birds had been sent to Mr. Buckland for 

 examination caused ine to look over my notes on the subject, made in the spawning 

 season of 1856-7. Up to that period I, in common with other preservers of salmon 

 and trout, took it for granted that, because this bird is so constant a visitor on the 

 salmon while that fish is spawning, it is solely for the purpose of feeding upon the ova, 



