HOW ANIMALS EAT. 51 



(2) Solids. When the food is in solid masses, whether 

 floating in water or not, the animal is usually provided 

 witli prehensile appendages for 

 taking hold of it. The jelly- 

 like Amceba has neither mouth 

 nor stomach, but extemporizes 

 them, seizing its food by means 

 of its soft body. The food then 

 passes through the outer wall 

 into the softer interior, where it 

 is digested. The waste particles with pseudopodia extended, x so. 

 are passed out in a similar way. In the Foraminifers, 

 thread-like projections of the body are thrown out (pseu- 

 dopodia) which adhere to the prey. The soft jelly-like 

 substance of the body then flows down the pseudopodinm, 

 collects about the food, and digests it (Fig. 15). 



A higher type is seen in Polyps and Jelly-fishes, which 

 have hollow tentacles around the entrance to the stomach 

 (Fig. 193). These tentacles are contractile, and, moreover, 

 are covered with an immense number of minute sacs, in 

 which a highly elastic filament is coiled up spiral h 7 (lasso- 

 cells, nettle-cells). When the tentacles are touched by a 

 passing animal, they seize it, and at the same moment 

 throw out their myriad filaments, like so many lassos, 

 which penetrate the skin of the victim, and probably also 

 emit a fluid, which paralyzes it; the mouth, meanwhile, 

 expands to an extraordinary size, and the creature is soon 

 engulfed in the digestive bag. 



In the next stage, we find no tentacles, but the food is 

 brought to the mouth by the flexible lobes of the body, 

 commonly called " arms," which are covered with hun- 

 dreds of minute suckers; and if the prey, as an Oyster, is 

 too large to be swallowed, the stomach protrudes, like a 

 proboscis, and sucks it out of its shell. This is seen in 

 the Star-fish (Fig. 126). 



