240 THE AQUARIAN NATURALIST. 



" niggers " are numerous, and get into the crab-pots, 

 it is very rarely that either crabs or lobsters are 

 caught. Their appearance, when closed up, very 

 much resembles a small cucumber, their back being 

 dark, almost black at times, and the under part light 

 yellowish green. Around the base of the tentacula 

 is a border of spines very much resembling the thorns 

 of the brier, and similar spines are distributed over 

 the creature's back. The under side of the body is 

 furnished with very numerous suckers, which they 

 can stretch out to a great length, and by their 

 means attach themselves firmly to foreign objects; so 

 much so, indeed, that in trying to detach the animal, 

 its suckers are not unfrequently left behind. Each 

 sucker is provided at its tip with a small round calca- 

 reous plate, which, under the microscope, forms a 

 very beautiful object. 



This species of Holothuria is extremely irritable, 

 and, on being touched or disturbed, throws out a 

 bunch of white taper threads about an inch in length. 

 These soon become attenuated, either by the agitation 

 of the water, or by coming into contact with extra- 

 neous substances, until they are drawn out into long 

 threads of great tenacity, which stick to everything 

 they touch, and hence the name of " cotton-spinners " 

 applied to these creatures by the fishermen. 



Night appears to be the chief season for enjoyment 

 and activity in these strange animals. Whatever be 

 their contracted state during the day, they expand 

 themselves at night, and display their beautiful arbo- 

 rescent tentacula at their utmost dimensions. Never- 

 theless, sometimes they will remain expanded through 



