THE METHOD OF CREATION OF ORGANIC FORMS. 213 



A curious case occurred to me in four species of fishes, which 

 I took in a small tributary of the Yadkin River, in Roane County, 

 N. 0, Among several others, there were varieties of the widely 

 distributed species Chaenohryttus viridis, Hypsilepis analostanus, 

 and Ptychostomus pidie7isis (each representing a different family), 

 which differ from the typical form of each in the same manner, 

 viz. : in having the back and upper part of the sides with longi- 

 tudinal black lines, produced by a line along the middle of each 

 scale. This peculiarity I have not observed in these species from 

 any other locality. Until I had examined them I thought them 

 new species. 



The only other species presenting such marking in the Yadkin 

 River is the large perch, the Roccus lineatus. According to the 

 theory of natural selection a resemblance to this well-armed species 

 might be of advantage to the much weaker species in question ; 

 yet the same species co-exist in other rivers without presenting 

 the same mimicry. 



It is difficult not to urge the importance of the causes already 

 regarded as efficient in the origination of structure in the present 

 branch of the subject also. We are especially disposed to call in 

 use and effort here, after noticing how much more distinctly 

 change of color is under the control of the animal, than change of 

 shape. It must, however, be borne in mind that similar resem- 

 blances exist among plants ; though, as Professor Dyer shows, a 

 large majority of these cases occur in species of different floral 

 regions. Thus in this case, as in those of structure already cited, 

 we appeal first to physical laws in the lowest beings, but with the 

 increasing interference of use, effort, and intelligence, as we rise in 

 the scale. Thus it is that, in the Vertebrates generally, the mi- 

 metic resemblances are found in species of the same region, where 

 only an intelligent or emotional agency could be illustrated. If 

 among animals as low as butterflies the influence of intelligence be 

 denied, that of admiration for the beauty, or fear of the armature, 

 of the predominant species imitated, would appear to be sufficient 

 to account for the result. Admiration and fear are possessed by 

 animals of very low organization, and, with the instincts of hunger 

 and reproduction, constitute the most intense metaphysical con- 

 ditions of which they are capable. But our knowledge of this 

 branch of the subject is less than it ought to be, for animals pos- 

 sess many mental attributes for which they get little credit. 



It appears to be impossible to account for the highest il lustra- 



