XXVII.] INSTINCT. 11 



how are we to account for the origin of so strange an instinct as Instincts 



that of the Arius, and of some other fishes, the male of which o' some 



' ' nsnes. 



hatches the eggs in his mouth ? ^ Questions of this sort, how- 

 ever, are neither more nor less difficult to answer than questions 

 concerning the origin of special structures, as for instance the 

 electric organs of some fishes ; a case which Darwin mentions 

 as one of special difficulty. 



^ Professor Turner, in British .Association Keport, 1866. 



