SUMMARY. S/ 



lations of the organic world represents the true one, 

 is admitted by all who have taken the trouble to 

 study into the matter. 



Recognizing that a classification exists, it is neces- 

 sary, if possible, to give some reason why it should 

 exist ; recognizing a unity, it is desirable to find 

 the bond of union. In answer, only two important 

 theories have been advanced the theory of types, 

 which finds the bond of union in the creating mind, 

 and the theory of evolution, which finds it in the 

 principle of descent. The first, in spite of the mas- 

 terly attempt of Agassiz to establish it, has been 

 constantly losing ground since the appearance of 

 the second. The impossibility of deciding even as 

 to the number of types, to say nothing of the im- 

 possibility of defining them ; the infinite number of 

 sub-types, and types within types, required to ex- 

 plain smaller groups ; the impossibility of finding a 

 position for many animals under any of the great 

 types ; the gradual approach of the groups toward 

 each other in their simpler and earlier forms, and 

 if embryology be taken as evidence, the union of 

 the sub-kingdoms, and kingdoms with each other, at 

 a common starting-point; and finally (and this has 

 in reality had more weight than the rest), the fact 

 that this explanation is a transcendental and not a 

 natural one ; all of these considerations have led to 

 the gradual abandonment of the theory of types. 



But the disproof of the first theory does not, of 

 course, prove the second. Each must stand on its 

 own merits, and not upon the disproof of the other. 

 We do find, however, that the evolution theory is 



