HOW ANIMALS EAT. 51 



(S) Solids. — When the food is in solid masses, wiiether 

 floating in water or not, the animal is usually .provided 

 with prehensile appendages for 

 taking hold of it. Tiie 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 tlie denser, outer 

 portion of the body into the soft- „ _ . „^. ,,„,,. ^ , , 



r _ •' _ riG.15.— A Rhizopnd {RotalmVenfta), 



er interior, where it is digested, wuh psendopocHa extendcei, x so. 

 The waste particles are passed out in a similar way. In 

 the Foraminifers, thread-like projections (pseudopodia) of 

 tiie body are thrown out whicii adhere to the prey. The 

 soft jelly-like substance of the body then flows toward and 

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



A higher type is seen in Polj'ps and Jelly-fishes, which 

 liave hollow tentacles around tlie entrance to the stomach 

 (Figs. 38 and 193). These tentacles are contractile, audi 

 some, moreover, are covered with an immense number of 

 minute sacs, in each of which a highly elastic filament is 

 coiled up spirally (lasso-cells, nettle-cells). When the ten- 

 tacles 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 vic- 

 tim, 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," whicli are covered with hun- 

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

 too large to be swallowed, tiie stomach protrudes, like a. 

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

 the Star-fish (Fig. 126). 



