12 



LECTURE V. 



Importance of simplest Animals. Of Animals living in Com- 

 munities, formed naturally into a common mass with a 

 common vitality; Sponge, Jllcyonium, Gorgonia,and Coral, 

 composed like the Hydra, of Cellular Tissue without special 

 organs. 



This Lecture, being almost exclusive demonstrative, and illus- 

 trated by impressive drawings and ^specimens, requires no analysis 

 to aid the memory. 



LECTURE VI. 



Same subject continued. Depuration of the Ocean. Influence 

 of the Polypi, or Zoophytes on Physical Geography. 



Impurities of the ocean. Influence of rivers, coasts, &c. 



Depths at which life may be maintained. Importance of 

 light to the zoophytes. 



Depuration of the waters by animals. Quarrelsome fellow- 

 travellers on sea-weed. Sources of lime employed by the 

 polypi of coral animals of the deep sea. Fish. Familiars 

 of vessels and wrecks. 



Polypi and other soft bodied animals, floating without sup- 

 port at sea; some with a community of life. Pyrosoma; 

 some merely associated by community of instinct. Salpa. 

 Origin of false shoals on charts. Submarine lightning. 



Great length of coral reefs in the Pacific Ocean. Probable 

 connection with the geological structure of the bottom. 



Influence of coral in extending lands. Best observed around 



volcanic islands. Isle of France. 

 Circular reefs of Pacific Are they connected with extinct 



craters? 



New islands built by coral Their form and progress In- 

 troduction of fresh water Formation of soil by marine 

 plants Massive sea-weed of Tristan d'Acunha Fuci of 

 Rhode Island Effects of the growth and decay of lichens, 

 mosses, and ferns Illustration The effects of the rainy 

 season on the appearance of buildings at Calcutta De- 

 struction of the very ruins of ancient cities by vegetation 



