1904.] PACKARD— ORIGIN OF MARKINGS OF ORGANISMS. 449 



We may suppose that by somewhat the" same process the shadows 

 cast on the bodies of primitive tigers, antelopes, reptiles, birds, 

 fishes, caterpillars, etc., produced stripes, bars and spots. I think 

 that these observations, coupled with the experiments of Steinach 

 and those of Poulton on the formation of pigment in the pupae 

 of butterflies, will enable us to understand how the markings of 

 animals arose. Keeble and Gamble add that the results obtained 

 with respect to background as the chief factor in inducing pigment 

 movement in Crustacea offer a curious and interesting parallel to 

 the results of Prof. Poulton, though for his word " formation " they 

 would substitute that of " movement." With this change the out- 

 come of Poulton's experiments " summarizes the state of affairs in 

 Crustacea." 



23. Conclusions. 



1. The alleged cases of Miillerian mimicry can be explained by 

 convergence due to the action of similar physical and climatic 

 causes. The attacks of birds are a negligible factor. 



2. The oftentimes striking and wonderful resemblances in colora- 

 tion and markings are the result of pigmentation caused by expo- 

 sure to the combined effects of sunlight and shade, and due — 



a. To the repetition of the fundamental colors, brown, black, 

 red, yellow, in insects of different orders, as well as animals of dif- 

 ferent classes, living exposed to direct sunlight, and often having 

 exceptional diurnal or light-loving habits in contrast with the luci- 

 fugous habits of the other species of the genus, family or order. 



b. The similarity of design appears in many, if not most, cases 

 to be due to the repetition of markings with identical shapes or 

 patterns, i.e., lines, bars, which are eventually broken up into spots 

 and repeated ad mfinitum, owing to the economy everywhere seen 

 in Nature of material and design, differing in details in different 

 groups, owing to their different origin and hereditary constitution. 



It is no wonder therefore that there should be apparent cases of 

 mimicry in regions like the hot and humid forest-covered plains of 

 Brazil and the East Indies, or the upland hot plains of southern 

 Africa, or in Australia where there are yellow flies, beetles and 

 Hymenoptera with a broad black band around the abdomen, hence 

 curiously mimicking each other. 



3. Extreme advocates of Batesian and Mullerian mimicry appear 

 to entirely overlook the operation of the physical agents of sunlight 



