THE TOMB OF PEARL 



They avoid the light, try to find dark corners, bury 

 themselves in the sand or hide in the crevices of rocks, 

 but especially they prefer the shelter of a living body, 

 provided always that they are assured of easy access. 

 There they find the shade of which they are so fond, 

 the protection which defends them, and, in addition, to 

 excite their own vitality, contact with another vitality 

 functioning at full strength. One species found in the 

 Mediterranean exhibits this characteristic in an aston- 

 ishing degree. 



This is the Needle Fierasfer, Fierasfer acus. It is 

 small, seldom exceeding five or six inches in length, 

 and, in breadth, only a fraction of an inch. Its long, 

 almost threadlike body, slightly flattened, ends in a 

 short, round head and a pointed tail. Almost all along 

 its length, its belly carries a longitudinal median fin, 

 like a thin, soft blade. Its skin has no scales, and is 

 smooth and occasionally bright. It justifies its generic 

 name Fierasfer, which Cuvier adapted from a Greek 

 word given to objects with a polished surface. It is so 

 transparent that all its main internal organs can be seen. 

 Everything goes to make the creature seem delicate, and 

 this especially in the young, which are practically trans- 

 lucent. They have above them a long nodular filament, 

 spread out like a crest, which later falls off and is not 

 found in the adult. 



The American Fierasfer sometimes shares the cavity 

 of the mantle of the pearl oyster, but the European 

 species, still more strangely, lives after the same manner 

 in the intestine of the sea cucumber, thus becoming 

 what is practically a parasite. It is, in fact, an 

 intestinal fish, as the tapeworm is an intestinal worm. 

 But there is an important difference; the worm 

 supports itself at the expense of its host, it 

 lives and has its abode in this way; it feeds upon 

 food which it takes from its host, whereas the fish 

 only accepts shelter, for it comes out at inter- 

 vals to seek food for itself, and then returns to its 



