178 The Life Story of the Fish 



man who has given the most study to the subject in Cali- 

 fornia recently has in essence this to say: 



The only difference between a steelhead and a rainbow is 

 in the migration to salt water. The adult steelhead is a trout 

 that has spent part of its life in the ocean, with the increase 

 in growth which accompanies such life. Young steelhead are 

 the offspring of these fish. Steelhead streams are those in 

 which the majority of fish are of this type, but may contain 

 trout which have reached maturity without leaving the 

 stream. And it may be that the hatch from eggs of this 

 latter type can become migratory. 



I know of no more complete answer to the old question. 

 To render it in terms of the Atlantic coast, the rainbow is 

 a "landlocked" steelhead. 



Further, it is now held that the dominant trout of the 

 Canadian Pacific coast, the Kamloops, is a form of the rain- 

 bow. The principal difference between them is the number 

 of scales, and it has been found that by raising the tempera- 

 ture of the water during the embryonic period Kamloops can 

 be produced with as few scales as the rainbow. The two are 

 merely climatic variations of the same fish. If we admit this, 

 we can tell ourselves a very complete, though entirely hypo- 

 thetical story. 



A certain fish at one time lived in the Arctic. He moved 

 south into the waters between Europe and America, and there 

 came to be called the Atlantic salmon. He moved south to 

 our Pacific coast, and there came to be called the steelhead. 

 He entered the streams of California and was known as the 

 rainbow 5 he entered the streams of British Columbia, and 

 was known as the Kamloops trout. He is at present engaged 

 in turning himself into several distinct kinds of fish, but the 

 distinctions are not yet very clear. Some day, unless man 

 interferes, they may be. The intergrading links will then 

 have disappeared, and we shall have sharply defined species j 



