20 PHILOSOPHY OF ZOOLOGY. 



eives and cresses, depends on the displays of this repairing 

 power. But the indications of its existence which have al- 

 ways appeared to me the most extraordinary, are exhibited 

 by trees. In a young silver-fir, (Plnus picea), for exam- 

 ple, I have seen the central vertical shoot cut off, so that the 

 tree must have ceased to increase in height, unless there had 

 been some repairing power, as the lateral branches invariably 

 expand in a horizontal direction. But one of these lateral 

 branches has begun to change its position ; and, by bend- 

 ing itself upwards, at last assumed a vertical direction, and 

 became the leading shoot and trunk of that plant, of which 

 it was formerly a subordinate branch. It has sometimes 

 happened, that more branches than one changed towards 

 the vertical direction, and thus rivalled each other in their 

 attempts to repair the loss of the original stem. 



Animals, as we have already stated, can, in many in- 

 stances, protect themselves from accidents, by resistance or 

 retreat. But, when wounded, this renovating power is 

 often exerted in an astonishing degree, in repairing lacerated 

 muscles, cementing broken bones, closing ruptured vessels 

 and supplying the loss of extravasated juices. In the 

 lower orders of animals, the loss of amputated parts is 

 speedily supplied by the production of new organs, as takes 

 place with the tails of serpents, and the claws of lobsters ; 

 or the detached parts, when placed in favourable circum- 

 stances, evolve themselves into separate and independent in- 

 dividuals, as is the case with the common fresh water polypus. 



It would have been easy to have multiplied examples of 

 the display of this instinctive power in repairing injuries, 

 were those which have been produced not sufficient to de- 

 monstrate its existence, and mark the characters by which 

 it is distinguished. 



4. Possessed of a Procreatlve Power. The power which 

 we have been considering, as displayed in the arrangement 



