the Coloration of Crustaceans. 147 



especially intrusted with this service, I have been enabled for 

 several years past to be present at the picking up of the buoys 

 included in the district of La Hougue : upon one of these it 

 was my fortune to observe an immense quantity of Gomntula 

 [Antedon rosacea) j with which the chain of the buoy was 

 literally covered. 



These specimens of Comatula were of three very distinct 

 colours — more or less deep violaceous red, orange-yellow 

 inclining towards saturn-red, and, lastly, alternately white and 

 red with whitish pinnules. Now I was not a little surprised 

 at observing along the chain ot the buoy specimens of tlippo- 

 lyte apparently living side by side with the feather-stars, which 

 they in many cases clasped with their limbs, and agreeing, at 

 least in the majority of instances, so closely with their neigh- 

 bour in colour that it became difficult to perceive them. 



The fact, strange as it is, is not unique. Lucien Joliet has 

 recorded a similar faculty in a Mediterranean Pontonia living 

 as a commensal with Diazona ; this Pontonia^ which is allied 

 to P. tyrrhena and which Joliet has described as a new species 

 inider the name P. diuzonce *, also bears a deceptive resem- 

 blance to the Diazona ; the transparency of its body blends 

 with the hyaline jelly of the colony, and the yellow spots with 

 which its thorax, abdomen, and chelas are marked harmonize 

 so perfectly with those of the Ascidian itself, that it becomes 

 impossible to perceive its presence so long as it remains upon 

 its host. 



Specimens of Palcemon also exhibit variations in colour 

 according to the nature of the bottom on which they are 

 found, becoming green when the bottom is covered witli 

 Zostera and grey or reddish yellow when the bottom is of 

 sand. 



Some years ago M. Georges Pouchet made some very 

 interesting observations upon this subject f. Taking some 

 earthenware vessels coloured black and white inside, he placed 

 in them for the purpose of observation some specimens of 

 Paloimon of medium size (8 to 4 centim. in length), which 

 experience had taught him to be most readily subject to 

 variations of colour. These prawns, which on leaving the 

 fishermen's nets are usually of a roseate or faint lilac tint, 

 become colourless, or at the most faintly yellowish, in tiie 

 vessels with a white bottom ; while in the black vessels they 

 become, on the contrary, dark brown. 



* L. Joliet, " Observations sur qiielques Crustaces de la Meiiterran^e," 

 Arch. Zool. exper. t. x. p. 118. 



t G. Pouchet, ' Journal d'Anatomie et de Physiologie/ 1872, t. iv. 

 pp. 401 -407 ; C. Ft. Acad. Sc. Paris, 20 mai, 1872. 



