TO DIGESTION OF ZOOPHYTES. 



years without eating. Their voracity is sometimes al- 

 most incredible. The Boa constrictor and Anaconda 

 swallow animals nearly as large as themselves, and af- 

 terwards retire to some obscure place, and remain in a 

 state of stupid inaction while the process of digestion is 

 going on. 



In the Mollusca, or shell-fish, the organs of digestion 

 present considerable variety of structure. Some of them 

 only have jaws for mastication. Some are provided with 

 a crop, and a muscular or membranous stomach as in 

 the Birds, and they are probably used for the same pur- 

 pose. Those without a head, as the clam, oyster, &ic. 

 feed only on such nutritious matters as are brought to 

 them in the water. The lobster, crab, &e. are remark- 

 able for having their teeth placed in the stomach instead 

 of their jaws. 



Emily. -An arrangement w T hich has one convenience 

 at least the creature is saved the trouble of moving 

 them. But, pray, how are they used ? 



Dr. B. They are situated on opposite sides of the 

 stomach near its lower end where it begins to grow nar- 

 row, and being moved up and down by the action of this 

 organ, they thoroughly grind up the food which passes 

 between them. 



In the Zoophytes where the whole internal parts of 

 the animal constitute the digestive cavity, there is no 

 distinction of the process into chymification, chy lification, 

 &,c. but it is all performed without any distinct stages, 

 and the chyle instead of being taken up by a particular 

 set of vessels, transudes through the sides of this cavity 

 and bathes the whole body. Some of the medusae instead 

 of a single mouth, are furnished with numerous branch- 

 ed feelers, each perforated by a small opening. Each 

 opening leads into a small canal which joins a neigh- 

 boring one, and so on till four large trunks are formed 

 which end in the stomach and convey to it the matters 

 absorbed by the apertures of the feelers. The number 

 of the latter is sometimes eight hundred. 



