SEXUAL SELECTION. 



[Part II. 



27.) In our salmon this change of structure lasts only 

 during the breeding-season ; but in the Salmo lycaodon 

 of Northwestern America the change, as Mr J. K. Lord 7 



Fig. 26.— Head of male of common salmon {Salmo salar) during the breeding- 

 season. 



[This drawing, as well as all the others in the present chapter, have been ex- 

 ecuted by the well-known artist, Mr. G. Ford, under the kind superintendence 

 of Dr. Giinther, from specimens in the British Museum]. 



7 "The Naturalist in Vancouver's Island,' vol. i. 1866, p. 54. 



