62 ANATOMY AND PHYSIOLOGY 



trout were nearly in a condition for spawning, he 

 caught both males and females in a net. By gen- 

 tle pressure of the hands, the ova were received in- 

 to a vessel of water. He then, by similar contri- 

 vance, forced the seminal liquor of the male into 

 the vessel, and after the two had been in this con- 

 dition only a few minutes, he placed the eggs in 

 his hatching box, to wait the result. At the expi- 

 ration of a few weeks, the parchment-like shells 

 burst — and to his unspeakable delight, the box 

 was swarming with an immense school of infant 

 trout. To each individual, was appended a httle sac, 

 which contained the yolk. This was their food 

 for a considerable time — being gradually taken 

 into the stomach, by the absorbing function of the 

 naval string. Here is a very striking analogy to 

 the provision, which is made for tl]e young of birds. 

 The yolk does not in any way become organized 

 in the process of incubation : — it was expressly 

 designed for the first food of the newly created an- 

 imal. Surely, this is an illustration of the homely 

 saying, '' that there is never a mouth without some- 

 thing to put into it." When the chick is hatch- 

 ed, the yolk is still as perfect, as before, but in- 

 stead of being in the old shell, it is now within the 

 body. Enclosed in a slightly elastic capsule, there 

 is a duct leading from it, that terminates in the 

 stomach. Through this, it continues flowing, as 



