ORGANS OF DIGESTION. 193 



louth to the ground, has the nose prolonged into a trunk, 

 which he uses with great dexterity, for bringing food and 

 drink to his mouth. Doubtless the mastodon, once so abun- 

 dant in the pre-Adamite earth, was furnished with a similar 

 organ ; man and the monkeys employ the hand, exclusively, 

 for prehension. 



349. Some animals drink by suction, like the ox ; others 

 by lapping, like the dog. Birds simply fill the beak with 

 r, then, raising the head, allow it to run down into the 

 crop. It is difficult to say how far aquatic animals require 

 r with their food ; it seems, however, impossible that they 

 should swallow their prey without introducing at the same time 

 some water into their stomach. Of many among the lowest 

 animals, such as the polyps, it is well known that they frequent- 

 ly fill the whole cavity of their body with water, through the 

 mouth, the tentacles, and pores upon the sides, and empty it 

 at intervals through the same openings. And thus the aquatic 

 mollusks introduce water into special cavities of the body, or 

 een their tissues, through various openings, while others 

 pump it into their blood-vessels, through pores at the surface 

 of their body. This is the case with most fishes. 



Besides the more conspicuous organs above described, there 

 are among the lower animals various microscopic apparatus 

 for securing prey. The lassos of polypi have been already 

 mentioned incidentally. They are minute cells, each containing 

 a thin thread coiled up in its cavity, which may be thrown out 

 by inversion, and extended to a considerable length beyond the 

 sac to which it is attached. Such lassos are grouped in clus- 

 upon the tentacles, or scattered upon the sides of the 

 actinia, and of most polypi. They occur also in similar clus- 

 ters upon the tentacles and the disc of jelly-fishes. The net- 

 tling sensation produced by the contact of many of these ani- 

 mals is undoubtedly owing to the lasso cells. Upon most of 

 the smaller animals, they acras a sudden, deadly poison. In 

 echinoderms, such as star-fishes, and sea-urchins, we find other 

 microscopic organs in the form of clasps, placed upon a move- 

 able stalk. The clasps, which may open and shut alternately, 

 are composed of serrated or hooked branches, generally three 

 in number, closing concentrically upon each other. With 

 ;pons, star-fishes not more than two inches in diame- 

 aud retain shrimps of half that length, notwithstand- 

 ing their efforts to disentangle themselves. 



o 



