1056 EEPOET OF COMMISSIONER OF FISH AND FISHEEIES. [12] 



living, and either orange or red. All these Anthozoa are furnished with 

 powerful stinging organs for offense and defense, so that their 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 aaay be of use bv concealing them from their 

 prey, whieh 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 aureiutiacaY .) which lives habitually as a com- 

 mensal, on Bolocera Tuedice, a very large orange-red actihian, with un- 

 usually powerful stinging organs. Doubtless the worm finds on this 

 account perfect protection against fishes and other enemies. This an- 

 nelid is of the same intense orange color as its actinian host. Such a 

 color is very unusual among annelids of this group, and in this case we 

 must 1 egard it as evidently protective and adaptive in a very complex 

 manner. 



It lias be(.'n urged by several writers that the light in the deep sea is 

 derived from the i)hosi)horescence of the animals themselves. It is true 

 that many of the deei)-sea Anthozoa, Hydroids. Ophiurans, and fishes 

 are phosi)horescent, and very likely this propeptyis possessed by mem- 

 bers of otht'r groups in which it has not been observed. But so far as 

 known, phosphorescence is chiefly developed in consequence of nervous 

 excitement or irritation, and is evidently chiefly of use as a means of 

 defense 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 jiossible for animals otherwise 

 defenseless to obtain i)rotection by acquiring this property. It is well 

 known to fishermen that fishes avoid nets and cannot be caught in them 

 if phos])hprescent jelly-fishes become entangle<l in the meshes. There- 

 fore it can hardly be possible that there can be an amount of phosphor- 

 escent light regularly evolved by the few deep-sea animals having this 

 power sufticient to cause any general illumination, or powerful enough 

 to have influenced, over the whole ocean, the evolution of complex eyes, 

 brilliant and complex protective colors, and complex commensal adap- 

 tations. 



It seems to me probable that more or less of the sunlight does actually 

 penetrate to the greatest depths of the ocean, in the form of a soft sea- 

 green light, perhaps at 2,000 to 3,000 fathoms equal in intensity to our 

 partially" moonlight nights, and possibly, at the greatest depths, equal 

 only to starlight. It must be remembered that in the deep sea, far from 

 land, the water is far more transparent than near the coast. 



