THE HOLOTHURIANS OF THE HAWAIIAN ISLANDS. 



By Walter K. Fisher, 



Of Stanford Lhiiversity, California. 



INTRODUCTION. 



Holothuiians or sea cucumbers are fairlj- plentiful in the tide pools 

 among- the lava rocks and on exposed reefs of the Hawaiian Islands 

 and form a very characteristic portion of the moi'c conspicuous shore 

 fauna. They are almost sure to be found l)y the general naturalist 

 who explores the reef between Honolulu and Waikiki or carries his 

 investigations to remoter parts of the islands among the many pools 

 and inlets that fringe the lava shores. Such forms as Actlnopyga 

 inaurltiana., IloJotliurla atra^ H. fuseoruhra., II. cinerascens.^ H. 

 permcax, II. pardalh^ H. hnpatiens., and Stichopus tropicalh are 

 common, especially the first two, which are large and take no pains to 

 hide themselves. In Pearl Harbor, Oplwodesoiiia spectaljlUx., which 

 occurs in great numbers, is likely to attract the attention of an3'one 

 interested in natural history. Careful and systematic collecting on the 

 reefs and in the tide pools should bring to light man}^ characteristic 

 tropical forms as yet unrecorded from the islands. Care should be 

 taken to turn over large stones and to examine masses of seaweed. 

 One form, at least, Chiridota hatcailensis., lives buried in coral sand. 



Holothurians are best preserved in fairly strong alcohol, rather than 

 in formalin, because the latter is likely in time to partially dissolve 

 the minute calcareous bodies which occur in the outer la3'er of the 

 body wall and which are a necessity for the accurate identification of 

 s])ecimens. To kill the animals in an expanded condition, it is well to 

 fii'st narcotize them by gradually adding to the sea water in which 

 they are contained a quantity of Epsom salts or about an equal volume 

 of ether. The latter should be added gradually after the animals are 

 expanded. When they are thoroughly numbed, they may be placed in 

 about 60 per cent alcohol and after a few hours transferred to 90 per 

 cent. Chloretone is a good narcotizing agent, but is expensive. 

 Some species are so sensitive that acid i-eagents must be resorted to in 



Proceedings U. S. National Museum, Vol. XXXII— No. 1555. 



637 



