10 THE BERMUDA ISLANDS. 



were compelled to desist from our attempt after the labor of a 

 full hour and a half. The chromatic changes of the skin were 

 at times very rapid, and so nicely did the animal adjust its 

 color to thiit of the rock as to render its outline barely visible. 

 The wonderful transparency of the greenish waters permitted 

 objects to be distinctly visible at depths of 20-25 feet, and where 

 there were no moving ripples, at even greater depths. I 

 doubt much, however, the statement that under ordinarily 

 favorable conditions objects may be distinguished at depths of 

 60 to 70 feet, even with the aid of the water-glass ; at any rate, 

 our own experience failed to give support to this commonly- 

 received notion. Almost everywhere within, the bounding 

 reef, except where special circumstances have favored the de- 

 velopment of coral and millepore patches, the bottom is largely 

 barren, presenting a nearly uniform expanse of coral sand. 

 This is the paradise of the sea-urchin (Toxopneustes variegatus) 

 and of the great black sea-cucumber which is so common in 

 the inner waters. Froni the anchorage of the Villa Frascati we 

 watched day after day the uncouth ebony masses of the latter, 

 scattered like so many black blotches over the sand. Onlj' ex- 

 ceptionally could they be observed to change their position, 

 although the rolls' of sand drawn over the surface indicated 

 that such changes were not uncommon ; not improbably their 

 perambulations take place largely at night-time, when their 

 movements would not be likely to attract attention. In the 

 normal condition of rest and apparent non-animality the creat- 

 ure might readily pass aggressive observation, even though 

 it be the most conspicuous object on the bottom ; and in thus 

 deceiving what might otherwise be formidable enemies it is 

 probably largely assisted by its forbidding black color. It is 

 a significant fact, although it may hold no special relation in 

 the matter, that another form of holothurian (like the latter, 

 new to science), of almost equal size, and with a ground color 

 of reddish-yellow, occupies the same haunts, but in vastly di- 

 minished immbers. Can it be that it is suffering extermina- 

 tion through the possession of a more attractive, even though 

 less apparent, coloration ? 



