ZOOLOGICAL APPLICATIONS OF THIS METHOD OF RESEARCH. 



333 



If we take for example the genera Cam's, Vulpes, and Urocyon of the 

 family Canidce, they will be found to be as closely related to each other in 

 regard to the crystallography of their hemoglobins as are the species of a 

 single genus in other cases ; for example, as the crystals from the baboons 

 of the genus Papio are to one another. Indeed, the dingo (Cam's dingo) 

 varies more from the normal dog type in regard to these characters than the 

 species of the genus Canis in general vary from the species of Vulpes and 

 Urocyon. Compare, for example, the axial ratios of the following species 

 of Canidce (table 52) : 



TABLE 52. Comparison of axial ratios of species of Canidce. 



An examination of these figures would seem to indicate that, in so far 

 as the crystallographic characters of the hemoglobins are concerned, the 

 Canidce examined should all belong to one genus. The fact that they readily 

 cross with each other is another argument in the same direction. 



Similarly, in the genus Felis and the related genus Lynx, the very close 

 relationship will be seen by a comparison of the crystallographic characters 

 of the hemoglobin. Take, for instance, the reduced hemoglobin crystals of 

 the cats and compare the axial ratios of this substance in the principal 

 species of Felis with the two species of Lynx studied: 



TABLE 53. 



Here again the correspondence is very close between the characters 

 of the reduced hemoglobins of the two related genera, and they have more- 

 over the same crystal habit as regards their oxy hemoglobin, which indicates 

 that this substance in the two genera is nearly the same material. 



If it is possible by an examination of such characters as the crystal- 

 lography of common vital substances in related genera or species to establish 

 systematic zoological relationships between them, it should be possible 

 to use such characters to test phylogenetic relationships. Some examples 

 of this sort of comparison of the crystallographic characters have already 

 been cited. The relation of the seals with the otters and of the sea-lions 



