SEXUAL SELECTIOX. 



[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 ^ 



Fig. 2G.— Head of male of common palmon (Salmo ealar) during the brceding- 



eeason. 



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

 ecnted l)y the well-known artist, Mr. G. Ford, under the kind superintendence 

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



'The Naturalist iu Vancouver's Island,' vol. 1. 1SG6, p. 54. 



