VARIATIONS AND GENETIC RELATIONSHIPS OF THE 

 GARTER-SNAKES. 



By Alexander G. Ruthven, 



Curator of the University Museum, University of Michigan, Ann Arbor. 



INTRODUCTION. 



In these times, when there is so great activity in evolutionary 

 research along all lines of biological work, it is important that sys- 

 tematic studies be directed so as to throw^ light on the problems 

 involved in the origin of species. An examination of the actual 

 sj^tematic work that has been done, however, can not fail to reveal 

 the fact that only a comparatively small amount of it has been done 

 with this end in view. This is especially true in the case of reptiles, 

 and more particularly in the order Serpentes, where but little work 

 has been contributed to this phase of the subject. Without doubt 

 one reason for this is to be found in the fact that the snakes are a 

 most perplexing group systematically, owing to the difficulty in 

 finding characters that are capable of defining natural groups. For 

 this reason but a comparatively small amount of work has been done 

 on the group. As Baird said in 1853 (1853, p. v.), "Systematic 

 workers all carefully avoid the subject of Ophidians, each waiting 

 for the others to make the first step;" and although in the fifty years 

 that have elapsed since this statement was made considerable work 

 has been done upon the order, and a multitude of forms have been 

 described as the result of the careful studies of Baird, Stejneger, Cope, 

 Garman, Brown, Van Denburgh, and others, only a ver}^ few con- 

 clusions have been reached as to the origin and descent of the forms. 



This barrenness of general results can not be entirely attributed 

 to a lack of facts, but must be inherent, to some degree at least, in 

 the methods employed. An examination of the systematic work 

 that has been done upon the snakes shows, as might be expected, 

 that it is largely analytical in its nature, being for the most part 

 descriptive of the existing diversities. That this kind of work is of 

 value can not be questioned, for, as has been well said by Tutt (1896, 

 p. 6): "The species describer, if he does his work intelligently and 

 carefulh', is giving the evolutionist the exact material on which alone 



1 



