160 CLASS-BOOK OF ZOOLOGY. 



QUESTIONS ON SECT. XLI. 



670. What are Infusory Animalcules ? 



671. How can they be obtained, and what will be the effect? 

 67-2. What will also furnish a great variety of them? 



673. How can it be proved that they are real animals? 

 074. Which is the smallest, and which the largest of these animals, 

 and where are they found ? 



675. What are Polypes? 



676. Of what does then food consist ? 



677. How dm they be obtained for examination ? 



678. Describe their body. 



679. Why is their construction and reproduction astonishing? 



680. What is their color, and how may they be kept alive '! 



681. Describe the Sea-blubber. 



682. What is their general color, size, form, and abode ? 



683. Of what use are they ? 



SECTION" XLII. 

 2J Order — Corals: (Corallia, Lin.} 



5 684. Corals are the horny or stony habitations of 

 small Sea-polypes. They are not, however, to be con- 

 sidered habitations, in a sense analogous to the cells of 

 Bees ; but rather resemble the shells of Snails, sinje the 

 young Sea-polype is produced simultaneously with its 

 calcareous dwelling, in the same manner that a twig is 

 pushed out from a tree. 



§ 685. The stony Corals in the torrid zone ascend in 

 large masses from the bottom of the sea towards the sur- 

 face of the water, and form small islands. Upon these 

 islands the tempestuous waves of the sea throw sand, 

 shells, and sea-weeds ; thus, in the course of time, form- 

 ing a soil, and rendering them habitable. 



§ 686. The injury sometimes done by Corals is con- 

 siderable. They often block up the channels of sea- 

 ports ; and when near the surface of the ocean, but not 

 sufficiently so as to be discoverable by the mariner, are 

 frequently the cause of shipwreck. 



