IOWA ACADEMY OF SCIENCES. 35 



white. This may also be true of bright red gorgonians, 

 pennatulidse and sponges, with their glassy spicules, and red 

 corals, with their very large nematocysts. 



The various cases of commensal association, such as the 

 ophiurians, resembling the brilliant gorgonians upon which 

 they climb, would thus be readily explained as instances of 

 protective resemblance. * Among the Crustacea the numerous 

 cases of bright red, red and white or green coloration may be 

 possibly capable of explanation along the lines of directive 

 coloration, whereby the individual may recognize its own 

 species, and thus the meeting of the sexes be facilitated. It 

 must be remembered that many deep-sea crustaceans have 

 excellent eyes. In short, these brilliant colors in all groups 

 can, according to this theory, be explained by reference to the 

 same laws that prevail on land or in shallow water. 



Beddard regards as a fatal objection to this theory the fact 

 that the eyes of many deep-sea dwellers are apparently now in 

 the process of degradation. But the same thing is found 

 among the mud-dwelling mollusca and the sponge-inhabiting 

 Crustacea, such as Alpheus in shallow water. Mud and sponges 

 are also found in deep water and have their inhabitants as 

 well. Again there are doubtless vast areas in which the phos- 

 phorescence is exceedingly feeble or entirely wanting, and yet 

 they are not necessarily or even probably tenant! ess. In such 

 places the possessors of eyes would find them worse than use- 

 less and gradual atrophy would ensue. I must confess to an 

 utter inability to see the force of Beddard's so-called "fatal 

 objection." 



A side-light is thrown on our discussion by some of the well 

 known facts concerning cave fauna. These facts are: 



First. — Cave animals are almost universally colorless, or at 

 least are not brightly colored. 



Second. — 1 have been unable to find any record of phosphor- 

 escence among cave animals. 



Third. — Blind animals are common in cave fauna. 



Fourth. — No cave animals, so far as I know, are character- 

 ized by greatly enlarged eyes. 



It would thus seem that the absence of phosphorescence in 



♦Beddard explains such cases by Saying- that the parasite actually assimilates and 

 deposits in its own skin the pigments of the host. (Loc. Cit., p. 38.) When we consider 

 that the colors of the gorgonians are in the hard and jagged spicules alone we cannot 

 withhold our sympathy from the ophiurian, which has either to eat such unattractive 

 fare or in some way to absorb it through the skin. 



