CHAPTER II. 

 THE MATERIALS. THEIR TAXONOMY AND NATURAL HISTORY. 



INTRODUCTION. 



The purpose of this chapter is to give as clear and complete an account of 

 the materials and their origin as is possible, so that no matter how taxonomic 

 groupings may change, there may be no uncertainty as to the characters, adult 

 and juvenile, and the actual locations from which my materials came. All 

 figures and descriptions are from the living animals, and are the species with 

 which I worked. The findings in experiment through this report are those for 

 a specific form, from a precise location in nature, and no more. I do not know 

 that the same " species " from another location would act the same in duplicate 

 experiments ; in fact, many of my experiences show that they do not, due to 

 diversity of the gametic composition of a phenotypical constant species that is 

 uniform in taxonomic aspect over its area of distribution, but is gameticaUy 

 dissimilar. Until we know more of the geographical distribution of this gametic 

 ■diversity, records must be for the reactions of specific materials from specific 

 locations, and not be applied broadly to phenotypieally uniform species. 

 ■Gametic uniformity must be proven and not assumed. 



METHODS OF OBTAINING MATERIALS. 



My materials without exception have been derived directly from nature, from 

 ■definitely located stations which have been under as constant observation as was 

 possible during the period in which the material was being used in the investi- 

 gation. 



In every instance where any material has been used in these experiments the 

 following routine has been followed : Having determined by preliminary tests 

 "that the species was of interest in connection with this investigation, I have 

 ihen, first, gone personally over the entire known geographical range of the 

 species in question, with the dual object of discovering its actual habitat and 

 .the geographic distribution thereof and the total range of variability of the 

 form both as regards its common fluctuations and accidental somatic aberra- 

 tions, and also to discover if, ia any restricted habitats, it had developed isolated 

 local races of any description. Further, I found it helpful to become acquainted 

 with all of the conditions under which any species was living and did live in 

 nature. Two sets of information concerning the species were thus obtained — 

 an extensive knowledge of the range of " variability " of the organism and at 

 the same time data of its conditions of existence. In itself this is no small task ; 

 it was further complicated and made difficult by the conditions prevailing in 

 Mexico and Central America, where much of this portion of the work had to be 

 done. 



At the same time that these field observations were in progress materials were 

 £ent in from the field to the laboratories at Tucson and Chicago, and there 

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