114 W. J. CROZIER. 



buried during the day about the roots of sea weeds. Its skin, 

 incidentally, is covered by a slimy coating of mud-particles, 

 tending to give it a concealing hue; whereas H. captiva, well 

 equipped with Cuvierian organs, but living under stones, is of a 

 brilliant dark green color, unobscured with mud. 



In feeding tests, the flesh of H. surinamensis was rejected as 

 vigorously as was that of Stichopus. 



It seems on the whole quite possible that some repugnatorial 

 property is present in the secretions of the holothurian skin. The 

 repellent power of the skin of the nudibranch Chromodoris zebra 

 has been amply demonstrated (Crozier, '16, and subsequent 

 work), yet I have found ostracods (Cypris) creeping freely over 

 its skin; and while the blue-black Ascidia atra is rejected, whole 

 or in fragments, by fishes I have tested, certain polyclads, 

 nevertheless, feed freely on its surface (Crozier, '17). It is not 

 inconceivable that the slimy quality of the holothurian flesh, 

 particularly as developed when the body wall is cut, is in itself 

 a sufficient repellent. I have never succeeded in inducing aqua- 

 rium fishes to swallow swollen pieces of gelatin, although in this 

 case a specific repellent action seems improbable. 



The adult Stichopus is, at all events, practically immune from 

 the grosser kinds of attack. The only dead or injured specimens 

 I have seen were killed by heavy rain-fall on shallow shores at 

 low tide, or else by the sun when left by the tide on an exposed 

 beach. The flesh of these animals is not an acceptable article of 

 diet to fishes or to octopus, and whether this immunity be due 

 in part to specific repugnatorial secretions, for which there is 

 some evidence, or to some physical property of the flesh, or to 

 the large size of the individuals, the feature which for present 

 purposes I regard as significant is this: although efficiently 

 protected, as it seems to be, the coloration of the species exhibits 

 a wide range of variation, such that in some instances it might be 

 thought "warning," in others decidedly "concealing." The con- 

 clusion is difficult to avoid, that the "conspicuous" type of 

 pigmentation is only associated with immunity from attack in a 

 secondary, and in a sense an accidental, manner. The flesh of the 

 paler, spotted, and as I believe, on the whole better concealed, 



