the Coloration of C I' ustacaans. 147 



esj)ccially intrusted witli this service, I liave been enabled tor 

 several year.s past to be present at the picking up of" the buoys 

 iiieluded in the district ot" La Ilou^ue : upon one of these it 

 was my fortune to observe an ininieuse quantity of Com i tula 

 [Antedon rosacea)^ with which tiie 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 llippo- 

 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 lJiazona\ this Pontonia, which is allied 

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

 under the name P. diazonce *, also bears a decej)tive 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 chelte 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 Pcdcemon also exhibit variations in colour 

 according to the nature of the bottom on which they are 

 found, becoming green when the bottom is covered with 

 Zostera and grey or reddish yellow wljcn the bottom is of 

 sand. 



Some years ago M. Georges Ponchet 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 

 Pahamon of medium size (3 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 

 lishermen's nets are usually of a roseate or faint lihic tint, 

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

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

 become, on the contrary, dark brown. 



* L. Joliet, " Observations surquelques Crustaces de laMeiilerranee,"' 

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



t (>. rouchtjt, 'Journal d'Anatoniie et de Phvsiologie,' 187:i, i.'w, 

 pp. 401 407; C. U. Acad. Sc. Paris, :>0 mai, 1871'." 



