376 AQUATIC VERTEBRATES 



with his pouch distended with eggs, he looks very much like a pregnant 

 animal about to give birth to offspring. It is sometimes said that this 

 is the only species of animal in which the male becomes pregnant. 

 When the eggs begin to hatch the male will hold onto a twig with his 

 tail and appear to go through all the pangs of labor as he brings forth 

 the living baby sea horses from his pouch. 



The Pacific salmon has one of the most complicated reproductive 

 cycles of them all. The adults are found in salt water, but they never 

 reproduce there. When they are ready to reproduce, which is at about 

 seven years of age, they will go into one of the fresh-water rivers that 

 empty into the Pacific. They are one of the few fish that are able to 

 make the transition from salt to fresh water without fatal reactions. 

 They continue up the river until they reach shallow spring-fed streams 

 far inland in which to spawn. The remarkable part about the whole 

 process is that they return to the identical stream where they were 

 hatched seven years previously. This can be determined by marking 

 the young salmon and checking their return. As they proceed up the 

 river they come to many forks and turns, waterfalls and rapids, but 

 nothing can stand in the way of their return to their place of origin. 

 When we are returning from a drive in the country and forget whether 

 to take the left hand or the right hand road when we just passed there 

 a short time previously, we can appreciate the salmons' problems in mak- 

 ing their way back. 



During their journey upstream they take no food and their mouths 

 become modified for digging their nests so that they could not eat if they 

 wanted to. Upon arriving at the breeding places they dig a nest over a 

 spot where a spring is bubbling up through the gravel, for such a spot 

 will not freeze during the severe winter which is found in northwestern 

 United States, western Canada, and Alaska. The eggs are then laid, the 

 sperms released over them, they are covered with gravel and the parents 

 flounder around awhile in the shallow water and die. The wolves and 

 vultures then have a feast, but the flesh is tough and stringy and not fit 

 for human consumption after the long exhaustive journey which the sal- 

 mon have made. They are caught in salt water for canning just before 

 they enter the rivers or shortly after they enter. When the young hatch 

 the following spring they slowly make their way downstream and reach 

 the ocean about a year later. 



Classification and Derivation of Scientific Words 



Subphylum Vertebrata (Cont.) 



Class A. Cyclostomata (Gr. cyclos, circle; stoma, mouth; refers to 

 the shape of the mouth). Lamprey eel. 



