4 
SEXUAL SELECTION. 
Paet II. 
“ the intermaxillary bones of tlie upper jaw.” 6 (Figs. 
26 and 27.) In our salmon this change of structure 
lasts only during the breeding-season ; but in the Salmo 
h/caodon of N.W. America the change, as Mr. J. K. 
Fig. 26. Head of male of common salmon (Salmo solar) during the breeding-season. 
[This drawing, as well as all the others in the present chapter, have been executed bv 
the well-known artist, Mr. (J. Ford, under the kind superintendence of Dr. Gunther from 
specimens in the British Museum.] 
6 Yarrell, 1 History of British Fishes, ’ vol. ii. 1836. p. 10, 
