13 



Vegetation aids in introducing moisture The spring of 

 La Pouce Mountain, in the Isle of France Seeds of trees 

 and shrubs introduced by birds and currents. The new 

 island takes the form of a ring of woods and a central 

 swamp. Becomes fitted for the residence of man. A 

 canoe and inhabitants. Primary agriculture. Volcanic 

 action raises mountains, arid the work is complete. 



The past. LyelPs Geology. Rise and fall of countries. 

 Changes marked by organic remains. Destruction of 

 races. Temple of Serapis in Italy. 



The future. Land and sea may again change places. Man 

 may yet owe the continuance of his species to the labors 

 of the zoophites. Importance of little things. Political 

 paraphrase. 



LECTURE VII. 



Of the Gradual Changes that take place in the Cellular Tis- 

 sue, as we advance toward the more Perfect Animals. The 

 manner in which this Tissue effects the Movements of the 

 Nutritive Fluid, and the first steps by which Special Organs 

 are formed in and by this Tissue. 



Cellular tissue strengthened by fibres How formed Its in- 

 fluence on the motions of the fluids. 



Skin thus strengthened Not classed with fibrous membranes 

 Why Its complexity in man It answers as a substi- 

 tute for a skeleton in many animals, as in medusa, shell- 

 fish The snail Its connection with the shell; its firm foot. 

 Strong adhesive powers of limpits and sea-ears. 



Fibres strengthening cellular tissue sometimes capable of be- 

 ing stretched and retracting Others firm and unyielding 

 They grow stronger by use Growth of skin over wens, 

 &c. Surgical applications of the principle. 



These cellular fibres exhibit the first step towards complexity 

 of structure. 



History of an animal composed of this complex cellular tis- 

 sue Physalia, or Portuguese man-of-war Its singular 

 manners and habits Origin of its motive powers Sup- 

 posed spontaneous division. 

 2 



