ORGANIC GEOLOGICAL DYNAMICS. 027 



there are characters which resist all the influences 

 both of external nature, of human intercourse, and 

 of time. 



Sect. 4. Hypothesis of Progressive Tendencies. 



WITHIN certain limits, however, as we have said, 

 external circumstances produce changes in the 

 forms of organized beings. The causes of change, 

 and the laws and limits of their effects, as they 

 obtain in the existing state of the organic creation, 

 are in the highest degree interesting. And, as has 

 been already intimated, the knowledge thus ob- 

 tained, has been applied with a view to explain 

 the origin of the existing population of the world, 

 and the succession of its past conditions. But 

 those who have attempted such an explanation, 

 have found it necessary to assume certain addi- 

 tional laws, in order to enable themselves to de- 

 duce, from the tenet of the transmutability of the 

 species of organized beings, such a state of things 

 as we see about us, and such a succession of states 

 as is evidenced by geological researches. And here, 

 again, we are brought to questions of which we 

 must seek the answers from the most profound phy- 

 siologists. Now referring, as before, to those which 

 appear to be the best authorities, it is found that 

 these additional positive laws are still more inad- 

 missible than the primary assumption of indefinite 

 capacity of change. For example, in order to 

 account, on this hypothesis, for the seeming adap- 



SS2 



