324 The Mechanism of Evolution in Leptinotaesa 



add another element to existing heterogeneity of race and form in nature. 

 These questions I have put to an experimental test as an aid in the further 

 analysis of the problems of heterogeneity in complex characters. 



PATTERN IN DIFFERENT HABITATS. 



In my 1906^ paper, under the terms "place variation" and " geograpliical 

 variation," I have discussed the differences found in the population in several 

 species of beetles belonging to this genus, using the current biometric methods 

 of expression and interpretation. Also, the experimental data then presented 

 were purely of the sort indicated by the quantitative, qualitative aspects of the 

 problems, although I then knew well enough that the whole aspect of the prob- 

 lem would soon change its setting and method of analysis. From the point of 

 view of the presentation in the 1906 paper nothing more is to be added to the 

 data and the conclusions there presented, and nothing further is to be expected 

 by continuation of the method of examination. Analyses had shown that all the 

 materials examined presented the phenomena of place variation in different 

 degrees, and the same species in the same place showed different variations, 

 depending upon the season. These biometric results and the legitimate deduc- 

 tions to be derived from them, with the experimental attempts to fix mere quan- 

 tity as measured statistically, while showing the presence of the condition with 

 regard to the phenomena and their difference in the several species examined, 

 lead to some points of view and conclusions that are essential to tie back to as a 

 part of the general problem that receives further analysis in this report. 



It was there recognized that on the basis of the results presented place varia- 

 tion was a generally present phenomenon in the organism examined, and also 

 in general that it affects every portion of the animal (p. 103), and that not all 

 animals are alike in their variability. The methods employed led to the con- 

 clusion that the " variations " were not germinal, but somatic fluctuations, the 

 product of the varying conditions of the environment (p. 102), and that some 

 of these conditions of the amount of pigment or other characters were in favor- 

 able instances to be rather accurately tied in interpretation to conditions in the 

 environment. The fact that in experiment the increase in the amount of 

 decrease was easy to produce, and had been produced in many experiments, led 

 to the conclusion with respect to the permanence of place variation that it was 

 not, as far as the evidence then went, permanent and a probable factor in the 

 production of evolution changes (p. 102). A possible correlation between the 

 production of extreme variations, simultaneous with the occurrence in the envir- 

 onment of divergent conditions, was noted, its possible action indicated from 

 actual examples, and its bearing upon the relation of these productions to 

 varying conditions, suggested lines of experiment (p. 104) . 



With respect to the condition as there measured by statistics, the conclusion 

 is valid as expressed, that the conditions thus determined were not permanent, 

 capable of fixation in experiment, and it is further true that many of the differ- 

 ences in the array of the measurements are mere ontogenetic exaggerations and 

 nothing more, due to the action of incident conditions at appropriate periods in 

 the life of the individuals. At present I fully concur in the result expressed in 



^An Investigation of Evolution in Chrysomelid Beetles of the Genus Leptino- 

 tarsa. Carnegie Inst. Wash. Pub. 48. 



