MODIFICATION OF COLOR. 2I3 



Among the long list of workers who have experimented upon Lepidoptera 

 with deviations of temperature and moisture, Weismann, Standfuss, and 

 Fischer stand preeminent as the most successful. Although each of these 

 workers obtained modifications which were produced in experiment and 

 inherited in succeeding generations, the fact that in the Lepidoptera used the 

 germ cells were in the more sensitive stages during the period of color for- 

 mation when the experiments were performed, leads one to conclude that the 

 apparent inheritance of somatic modifications was due to the direct result of 

 stimuli applied to the germ cells, and not to the inheritance of somatic modi- 

 fications. Superficially somatic and germinal variations are often indis- 

 tinguishable, but their different nature is shown in heredity. It is a fact, the 

 importance of which can not be overestimated, that out of the thousands of 

 experimentally produced color variations {somatic variations) recorded in the 

 literature of the last fifty years, as also in the experiments described above, 

 not one case of the unquestionable inheritance of such modifications has been 

 described. This fact is a most difficult one for the neo-Lamarckian to explain 

 away, because in it lies the direct experimental refutation of their cardinal 

 principle. 



In a large portion of the published work along the line of the experimental 

 modification of color the experiments described have been of too short dura- 

 tion to be productive of any generally reliable results. Many workers have 

 been contented to produce "aberrations," which have been interpreted as 

 atavistic repetitions of ancestral stages (Dixey, Merrifield), without any atten- 

 tion being given to the question of the natural variability and its direction 

 in the species experimented upon. There has been also a marked tendency to 

 ascribe specific effects to both temperature and moisture; whereas, as both 

 Fischer and I have shown, like results are produced by diverse stimuli. In 

 this connection it must be kept in mind that the experiments of Weismann, 

 Edwards, and others with dimorphic species of butterflies are not to be com- 

 pared with the experiments herein described ; because in their experiments it 

 is the production of changes in the alternation of dimorphic generations 

 that is brought about by experiment, and this is a phenomenon in no way 

 associated with the experimental modification of coloration in non-dimorphic 

 species. 



From the above-described experiments with Leptinotarsa I have drawn the 

 following conclusions, which are, I believe, generally true for all insects. At 

 least, all published data, on careful analysis, falls directly in line with these 

 conclusions, although often it is not so interpreted by its authors. 



(i) The different factors of the environmental complex do not have any 

 specific influence upon coloration, but all act alike as stimuli, either alone or 



