2 BULLETIN 61, UNITED STATES NATIONAL MUSEUM. 



any stable conclusions can be drawn with precision, and, if his work 

 is thus valuable, we must still recognize, nay, welcome, those who 

 give their best powers to the unraveling of the species in their multi- 

 tudinous forms, since these form the basis of all advanced evolution- 

 ary study." Wliile the value of the analytical method must, there- 

 fore, be admitted, its limitations should be clearly seen. Needless 

 to say it is not a knowledge of the present conditions alone that is 

 necessary, which is all that the application of this method can yield, 

 but a knowledge of the processes that have brought them about, for 

 systematic work can only become a true science when it seeks to 

 formulate the laws involved in the history of the present forms. 



The history of a particular form can not be worked out by determin- 

 ing its characters alone, but its affinities must be sought for, by 

 determining its similarities with other forms, and the factors which 

 influence it, before its derivation can be discovered. After analysis, 

 therefore, as has been said, comes the need of a larger synthesis. 

 This argument is often verbally granted by systematists, who, how- 

 ever, still adhere to the analytical method with the plea that a suf- 

 ficient body of facts has not as yet been accumulated upon which to 

 base general conclusions. This may probably be said of snakes 

 with more truth than for many other groups, but, when it is noted 

 that the work that has been done ofl'ers very little material upon which 

 to base such general conclusions, it would seem that a few generaliza- 

 tions based upon such limited material as is now available might in 

 many cases go far toward directing the course of future analytical 

 work toward better results. In the words of Meldola (1896, p. 7), 

 "However large the number of facts, and however cautious or con- 

 servative the worker may be, it is an established doctrine, taught 

 by the whole history of science, that real progress begins when we go 

 to seek for facts armed with at least the suggestion of a principle if 

 not with a complete theory based on facts already accumulated by 

 observation or experiment." 



Furthermore, it seems to be evident that any comprehensive 

 attempt to do synthetical systematic work must be made upon a 

 geographic basis, for the interrelations between the organisms and 

 their environments arc such that the history of the present forms is 

 involved with the history of the conditions with which they are associ- 

 ated, and affinities can only be sought in the light of geographic 

 probability. As Adams (1902a, 356) puts it, "It should be apparent 

 that in the past history of a region the conditions and highways must 

 be taken into consideration if we wish to understand the origin and 

 migrations of the diverse elements which enter into the fauna and 

 flora of any given region." As a study of the interrelations between 

 organisms and the natural environment, geographic distribution 



