396 CIRCULATION OF BLOOD IN FISH JUST HATCHED. 



vesicle) (see engraving) is too heavy for them', and soon 

 brings them to the bottom, Hke a bullet at the end of a 

 " paternoster " fishing-line. So far so good, but cannot 

 we see and learn more about these young fish ? Get out 

 the microscope, and place a new born salmon under a 

 low power, and you shall see one of the most beautiful 

 sights ever beheld by human eyes (see engraving). You 

 shall see the tiny heart (a), which is situated just un- 

 derneath 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 at the other side of the heart, and so it goes 

 on day and night, never ceasing, never tired — a great 

 forcing pump propelling the blood 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 ; I wonder how much it increases as he gets 

 older ? Just below the heart can be seen in the umbili- 

 cal 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 great blood 

 vessel ; with a high power you can see plainly the minute 

 blood-discs coursing along between the walls of the 

 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-discs, 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 streaks 

 (b B b) ; the microscope shows that these also are blood- 

 vessels, and that the blood in the one is running towards 

 the head, in the other toward the tail. A more complete 



