Narrative of Bahama Expedition. 213 



ment. I have watched them dismember in a large glass ves- 

 sel, when there appeared to be no rational incentive whatever 

 for such conduct. The Ophiurid.c were for some reason 

 almost entirelv overlooked in our work at this place. Ophiiira 

 cinerea Lyman being the only species saved. 



The coral rock out on the reef was fairly riddled with 

 holes made bv the black sea-urchin, Diadema setosiim Gray, 

 portions of the old decomposing coral heads presenting a 

 honev-combed appearance after the urchins have been re- 

 moved. When occupying these retreats, the animals have the 

 spines all directed outward in a great bunch, making a defen- 

 sive armature that would certainly prove effective against 

 almost any foe. How these animals, with their exceedingly 

 brittle and slender spines and unusually thin, fragile tests, 

 manage to make these excavations is something of a mystery-. 

 It mav be noted, however, that the teeth of Diadema setosnm 

 are verv strong, and the jaws capable of much more extensive 

 protrusion from the test than in most other species. These 

 teeth can be extended at least an inch beyond the corona, and 

 seem to me to be the means by which the borings are made. 

 HHyponoe escnlenta A. Ag. is found in countless numbers on 

 the sand-flat east of the island on which Spanish Wells is 

 located. This beautifullv white species is an excellent one 

 upon which to observe the •• righting movements" and other 

 experiments described by Romanes in his ver\- suggestive 

 work on ■•Jellv-Fish. Star-Fish and Sea-Urchins."' Some of 

 the experiments made during mv previous visit are perhaps of 

 sufficient interest to note in this connection. These animals 

 remove their excrement, which is in the shape of hard, rounded 

 bodies and is ejected from the apical region, by means of a 

 combined wriggling of the spines and pedicellaria?. Some of 

 these balls were dipped in acetic acid and then placed on the 

 apex of the test. There ensued a violent motion on the part 

 of the spines and pedicellaria\ and the irritating substance was 

 quicklv passed on lines radiating from the apex along the 

 ambulacral areas and dropped from the equatorial region of 

 the test. It appeared, therefore, that these organs worked in 



