ZOOLOGY: W. H. LONGLEY 
609 
onset of rigor exaggerated the condition existing prior to death and the 
animal stiffened in the characteristic postures. This follows the rule for 
rigor mortis, that the more strongly acting muscles contract more 
strongly after death. This fact lends additional proof for the tonus 
theory of the tropisms. 
Conclusion. — These experiments remove, in our opinion, the last 
doubt that the motions of animals to or from a source of light are due to 
an influence of the light on the tension of muscles of different sides of 
the body whereby the animal is automatically carried to or from a 
source of light. 
1 Loeb, J., WUrzburg, Sitz-Bcr. physik.-med. Ges., 1888; Der Heliotropismus der Tiere und 
seine tjbereinstimmung mit dem Heliotropismus der Pflanzen, Wiirzburg, 1889. 
2 Bancroft, F. W., /. Exp. ZooL, Wistar Inst., Philadelphia, 15, ,1913, (383). 
3 Loeb, J., and Maxwell, S. S., Arch. ges. Physiol. Bonn, 63, 1896, (121). 
*Loeb, J., and Garrey, W. E., Ihid., 65, 1896, (41). 
^Loeb, J., The Organism as a Whole, New York, 1916, pp. 257-259. 
« Holmes, S. J., /. Comp. Neiir. and Psychol., Wistar Inst., PhiladelpTtia, 15, 1905, (305).' 
^ Parker, G. H., Mark Anniversary Volume, 1903, (453). 
^ Mast, S. O., Light and the Behavior of Organisms, 1911. 
^ Moore, A. R., and Kellogg, F. M., Biol. Bull, Wood's Hole, Mass., 30, 1916, (131). 
CHANGEABLE COLORATION IN BRACHYURA 
By W. H. Longley 
GOUCHER COLLEGE. BALTIMORE. AND DEPARTMENT OF MARINE BIOLOGY. CARNEGIE 
INSTITUTION OF WASHINGTON 
Communicated by A. G. Mayer. September 10, 1917 
Although changes in coloration have been observed commonly in 
Crustacea, only two recorded cases appear to refer to Brachyura. Fritz 
Miiller reported to Darwin^ that the male of a Brazilian species of 
Gelasimus is subject to rapid and remarkable changes in appearance. 
R. P. Cowles^ has also described changes in color in Ocypoda arenaria 
Say, which he believes are in the main, if not entirely, dependent upon 
changes in the intensity of the light and variations in the tempera- 
ture to which the creatures are exposed. It would seem, however, 
that crabs are able at least to change their shade much more com- 
monly than recorded observations would indicate and that other fac- 
tors than those suggested may determine their coloration at a given 
moment. 
Portunus depressifrons Stimp., Callinectes ornatus Ord. and C. mar- 
ginatus A. M.-Edw. display striking changes in coloration under cer- 
tain conditions. Others less obvious or less closely studied have been 
noted too in Portunus spinicarpus Stimp. and P. sayi Gibbes and in 
