2l8 



Marvels of the Universe 



is a simple opening, and sometimes it is a veritable snout. In such forms the under side is 

 entirely different from the upper, either owdng to its flattened form, or to the nature of its 

 appendages. These may consist of little openings, sometimes of long tentacles, which, however, 

 are of no use for locomotion. There are some which have no appendages of any sort, and some 

 which crawl about on the ocean-bed after the manner of slugs. 



Besides these species, there are in the great depths some which live all but entirely buried 

 in the mud, where they remain almost completely motionless. On this account their bodies 

 have been absolutely changed as to symmetry. In the examples shown on page 220 it has 



taken the form of a U, so 

 as to bring the two digestive 

 orifices outside the region of 

 the mud. 



The Sea Cucumbers of 

 which we have spoken have 

 very peaceful manners. But 

 there is one which has dreamt 

 of vast spaces and the greatest 

 liberty. It has, therefore, be- 

 come a swimmer, or, rather, a 

 sea-navigator. It gets to the 

 upper seas and balances itself 

 gently on the waves. Different 

 conditions of life have altered 

 the structure of its body. 

 The species illustrated on page 

 214 is the only one at pre- 

 sent known that has taken 

 to the Jelly-fish's form and 

 habits. 



There is a remarkable cir- 

 cumstance connected with the 

 Sea Cucumbers, though it 

 is a story in which they take 

 but a passive and probabh- 

 unwilling part. The hinder 

 opening of the Sea Cucum- 

 ber's body contains extensive branching organs known as the respiratory tree, because within 

 it circulates the creature's blood and absorbs oxygen through its walls. To keep up this 

 supply of oxygen, sea-water is drawn in at short intervals, and expelled when the oxygen has 

 been extracted from it. Taking advantage of these openings, a small fish, known as the 

 Fierasfer, is said to enter the interior, and, turning, remains there with its head at the entrance 

 ready to pounce upon any suitable food that comes by. The story has been doubted by some, 

 and probabty it stands in need of corroboration. It is a curious story, for it is neither a case of 

 parasitism or of what is called commensalism, such as those examples of partnership described 

 in relation to the Hermit Crabs and the Ant-nest Beetle. The Fierasfer takes nothing from the 

 Sea Cucumber ; neither does he confer any benefit upon it : therefore, he is neither a parasite nor 

 a messmate. 



The Fierasfer is a thin, ribbon-like fish, about si.x inches long. 



ANCHORS AND GRATINGS. 



These remarUable object s^which are here shown much enlarged — are found 

 embedded in the skin of certain members of the Sea Cucumber family. Each 

 particular species has its own peculiar forms. 



