56 SCIENCE SKETCHES. 



As the season advances, the difiference between 

 the males and females becomes more and more 

 marked, and keeps pace with the development of 

 the milt, as is shown by dissection. The males 

 have (i) the premaxillaries and the tip of the lower 

 jaw more and more prolonged, both of the jaws 

 becoming finally strongly and often extravagantly 

 hooked, so that either they shut by the side of 

 each other like shears, or else the mouth cannot be 

 closed. (2) The front teeth become very long and 

 canine-like, their growth proceeding very rapidly, 

 until they are often half an inch long. (3) The 

 teeth on the vomer and tongue often disappear. 

 (4) The body grows more compressed and deeper 

 at the shoulders, so that a very distinct hump is 

 formed ; this is more developed in Oncorhynchus 

 gorbtischa, but is found in all. (5) The scales dis- 

 appear, especially on the back, by the growth of 

 spongy skin. (6) The color changes from silvery 

 to various shades of black and red, or blotchy, ac- 

 cording to the species. The blue-back turns rosy 

 red, the dog salmon a dull blotchy red, and the 

 quinnat generally blackish. The distorted males 

 are commonly considered worthless, rejected by 

 the canners and salmon-salters, but preserved by the 

 Indians. These changes are due solely to influences 

 connected with the growth of the reproductive or- 

 gans. They are not in any way due to the action 

 of fresh water. They take place at about the same 

 time in the adult males of all species, whether in the 

 ocean or in the rivers. At the time of the spring 

 runs all are symmetrical. In the fall all males, 

 of whatever species, are more or less distorted. 



