Kendall. — Blue Pike and Yellow Pike 265 



of which I have mentioned, suggest possibiHties of our being 

 able to find positive proofs of the structural divergence of 

 these two forms, not depending upon immediate ecological 

 relations, but of phylogenetic significance. Some of the dis- 

 tinctive features, such as that of the size of the eye, indicate 

 that the blue pike maintains youthful characteristics, as judged 

 by the young of the yellow pike, in well-advanced maturity. 

 So, while there are no specific differences recognizable by the 

 ordinary methods of the systematist, there is in each an 

 aggregate of correlated small differential characteristics. The 

 fish are constructed on two somewhat different models, so to 

 speak, the yellow pike on the whole being the more symmetrical. 

 The adult blue pike resembles younger yellow pike, and is 

 more variable than the yellow pike. Except in color, there 

 appears to be scarcely a single characteristic in the one, so 

 far as the inadequate number of specimens examined reveals, 

 that is not found in the other; but it is believed that even with 

 the specimens at hand, a careful study of the tables of measure- 

 ments, combined with age determination by means of the 

 scales, will show that all blue pike will differ constantly from 

 yellow pike of corresponding ages. If so, what does this fact 

 mean? To me, the youthful, and more generalized character- 

 istics suggest that the blue pike is a retarded development more 

 closely resembling the ancestral form of the species. It is pos- 

 sible to absolutely prove this point only through biometrical 

 studies of a large amount of material, and by study of the 

 life history, habits, and geographical distribution of the pike 

 perches. Particularly should the geographical limits of the 

 blue pike be defined. 



Yet this limited amount of study has revealed that the 

 blue pike are not all young and immature fish; that the color 

 appears to be constantly correlated with certain though small 

 differences of structure; and that blue pike, even as small as 

 some immature yellow pike, are mature fish. So, whether or 

 not taxonomical rules permit them to be endowed with a bi- 



