SHOE TEE ARTICLES AND DISCUSSION 



NOTE ON THE COLORATION OF PLANES MLNUTUS 1 

 It is well known that the coloration of the grapsoid crab Planes 

 nnnuhrs. a constant member of the Sargassum fauna, is ''homo- 

 chromic" to a high degree, not only as to tint and mottling, but 

 also in the frequent occurrence of a blotch of pale yellowish or 

 blank white upon the carapace: this lias Generally been supposed 

 to be a mimicking of the white patches of encrusting bryozoa and 

 Spirorbis tubes, which commonly infest the Sargassum. 2 . Ex- 

 periments made to discover the extent of possible color changes 

 in the adult Planes when it is placed over variously pigmented 

 artificial bottoms have led to no result, other than to show — con- 

 formably with what is known for some other Crustacea possessing 

 a dense body pigmentation, as contrasted with a relatively scanty 

 supply of well-scattered chromatophores — that the power of 

 color adaptation is decidedly limited. It is, therefore, of interest 

 to make record of an instance in which pronounced color adapta- 

 tion of Planes had occurred in nature. 



In January, 1916, after a rather severe gale, there was found 

 stranded upon one of the reef "heads" at Bermuda a large 

 "Spanish cedar" tree. It is certain that the tree had been in 

 the sea for some time, as the surface layer was thickly populated 

 by Teredo and boring amphipods. The trunk, the stumps of the 

 roots and the submerged branches of the tree were covered with 

 a forest of barnacles, Lepas anatifera, from among whose smoky- 

 brown erectile peduncles were obtained a vast number of adult 

 Planes minutus that were adhering to the more or less honey- 

 combed parts of the exposed bark and wood. Without excep- 

 tion the crabs were deep brownish-red, save for the frei|uently 

 occurring dorsal white patch. This pigmentation harmonized 

 precisely in general tint with the mahogany-colored surface of 

 the cedar tree. 



The interest of this case lies in its demonstration that these 

 crabs — prominent members of that specialized gulf-weed fauna 

 which has been urged as part of an argument for the antiquity 



