July 4, 1884.] 



SCIENCE, 



of the deep-sea species. In general, it may 

 be said that a large proportion of the deep-sea 

 animals are highly colored, and that their colors 

 are certainly protective. Certain species, be- 

 longing to different groups, have pale colors, 

 or are translucent, while many agree in color 

 with the mud and ooze of the bottom ; but 

 some, especially among the fishes, are very 

 dark, or even almost black ; most of these are 

 probably instances of adaptations for protection 

 from enemies, or concealment from prey. But 

 more striking instances are to be found among 

 the numerous brightly colored species belong- 

 ing to the echinoderms, decapod Crustacea, 

 cephalopods, annelids, and Anthozoa. In all 

 these groups, species occur which are as highly 

 colored as their shallow- water allies, or even 

 more so. But it is remarkable that in the 

 deep-sea animals the bright colors are almost 

 always shades of orange and orange-red, oc- 

 casionally brownish red, purple, and purplish 

 red. Clear yellow, and all shades of green 

 and blue colors, are rarely, if ever, met with. 

 These facts indicate that the deep sea is illu- 

 minated only by the sea-green sunlight that 

 has passed through a vast stratum of water, 

 and therefore lost all the red and orange rays 

 by absorption. The transmitted rays of light 

 could not be reflected by the animals referred 

 to, and therefore the} 7 would be rendered in- 

 visible. Their bright colors can only become 

 visible when the} 7 are brought up into the white 

 sunlight. These bright colors are therefore 

 just as much protective as the dull and black 

 colors of other species. 



The deep-sea star-fishes are nearly all orange, 

 orange-red, or scarlet, even down to three thou- 

 sand fathoms. The larger ophiurans are gener- 

 ally orange, orange-yellow, or yellowish white ; 

 the burrowing forms being usually whitish or 

 mud-colored, while the numerous species that 

 live clinging to the branches of gorgonians, 

 and to the stems of Pennatulacea, are generally 

 orange, scarlet, or red, like the corals to which 

 they cling. Among such species are Astrochele 

 Lymani, abundant on the bushy orange gor- 

 gonian coral, Acanella Normani, often in com- 

 pany with several other orange ophiurans 

 belonging to Ophiacantha, etc. Astronyx Love- 

 ni and other species are common on Pennatu- 

 lacea, and agree very perfectly in color with 

 them. These, and numerous others that might 

 be named 5 are instances of the special adapta- 

 tions of colors and habits of commensals for 

 the benefit of one or both. Many of the large 

 and very abundant Actiniae, or sea-anemones, 

 are bright orange, red, scarlet, or rosy in their 

 colors , and are often elegantly varied and striped , 



quite as brilliantly as the shallow-water forms ; 

 and the same is true of the large and elegant 

 cup-corals, Flabellum Goodei, F. angulare, 

 and Caryophyllia communis, — all of which 

 are strictly deep-sea species, and have bright 

 orange and red animals when living. The 

 gorgonian corals of many species, and the 

 numerous sea-pens and sea-feathers (Pennatu- 

 lacea) , which are large and abundant in the 

 deep sea, are nearly all bright colored when 

 living, and either orange or red. All these 

 Anthozoa are furnished with powerful stinging- 

 organs for offence and defence ; so that then- 

 colors cannot well . be for mere protection 

 against enemies, for even the most ravenous 

 fishes seldom disturb them. It is probable, 

 therefore, that their invisible colors ma}' be of 

 use by concealing them from their prey, which 

 must actually come in contact with these nearly 

 stationary animals, in order to be caught. 

 But there is a large species of scale- covered 

 annelid (Polynoe aurantiaea Verr.) which lives 

 habitually as a commensal on Bolocera Tue- 

 diae, a very large orange or red actinian, with 

 unusually powerful stinging-organs. Doubt- 

 less the worm finds, on this account, perfect 

 protection against fishes and other enemies. 

 This annelid is of the same intense orange color 

 as its actinian host. Such a color is very un- 

 usual among annelids of this group, and in 

 this case we must regard it as evidently pro- 

 tective and adaptive in a very complex man- 

 ner. 



It has been urged by several writers, that 

 the light in the deep sea is derived from the 

 phosphorescence of the animals themselves. It 

 is true that many of the deep-sea Anthozoa, 

 hydroids, ophiurans, and fishes are phosphores- 

 cent ; and very likely this property is possessed 

 by members of other groups in which it has 

 not been observed. But, so far as known, 

 phosphorescence is chiefly developed in conse- 

 quence of nervous excitement or irritation, and 

 is evidently chiefly of use as a means of defence 

 against enemies. It is possessed by so many 

 Anthozoa and acalephs which have, at the same 

 time, stinging-organs, that it would seem as 

 if fishes had learned to instinctively avoid all 

 phosphorescent animals. Consequently it has 

 become possible for animals otherwise de- 

 fenceless to obtain protection by acquiring 

 this property. It is well known to fishermen 

 that fishes avoid nets, and cannot be caught in 

 them if phosphorescent jelly-fishes become en- 

 tangled in the meshes : therefore it can hardly 

 be possible that there can be an amount of 

 phosphorescent light, regularly and constantly 

 evolved by the few deep-sea animals having 



