June, 1905.] Packard : Color in a Flower Spider. 95 



of thousands or great multitudes of individual spiders living on the 

 golden rods of avast area extending over northeastern America appear 

 to become similarly affected when the golden rods come into flower. 



In this case the color is not necessarily hereditary, since the young 

 spiders are at first colorless, and when older whitish. The yellow hue 

 persists only as long as the flowers are in blossom. Thus the yellow 

 color variety persists only as long as the colorational environment is 

 the same. Hence the natural selection theory seems quite inadequate 

 and also unnecessary to account for the apparent mimicry, and the 

 change of color is a clear case of adaptation to a color-environment, 

 and is an example of Lamarckism, or what Eimer and others call or- 

 thogenesis. 



Since this paper was sent for publication, we have read Keeble and 

 Gamble's elaborate memoir on the color physiology of the higher 

 Crustacea which fully confirms our view that color changes are pri- 

 marily due to light and environmental changes. The change of color 

 in the flower spiders seems to be an example of what Pouchet calls the 

 " chromatic function." He experimented by placing shrimps {Pal<z- 

 mon and Crangon) in black and white dishes in broad daylight. On 

 the black background the pigment cells expanded, and the resultant 

 coloration was a dark one in harmony with the tone of the surround- 

 ings. On the white background they contrasted, and the consequent 

 colorless place presented no contrast to the adjacent surfaces. Pouchet 

 claims that the pigment movements were due to the stimulus of light, 

 eletricicty and certain drugs, and he concluded that the background or 

 color of the environment determined the movements of the chromato- 

 phores or pigment cells, through the mediation of the eye and nervous 

 system. 



His results have been confirmed and extended by Keeble and Gam- 

 ble * in their recent work, from which we have taken the above ab- 

 stract of Pouchet's results. They also record that Jourdain (1878) 

 pointed out that in addition to light, electrical and pharmacological 

 stimuli, the temperature of the water influenced the color of sensitive 

 Crustacea, and that such changes were naturally independent of the 

 action of the retina. Keeble and Gamble have shown (1900) that 

 "rapid movements in the chromatophore could be induced by any 

 * decided stimulation ; that slow changes followed the application of 



* Phil. Trans. Roy. Soc. London, vol. 196, pp. 295-388. 1904. 



