We had no more reason to look for intermediate or 

 connecting forms between such types as these, than be- 

 tween any others of similar degree of remove from each 

 other with which we are acquainted. And inasmuch as 

 almost all groups, as genera, orders, etc., which are held 

 to be distinct/tut adjacent, present certain points of 

 approximation to each other, the almost daily discovery 

 of intermediate forms gives' us confidence" to believe 

 that the pointings in other cases will also be realized. 



y. Of Transitions. 



The preceding statements were necessary to the com- 

 prehension of the supposed mode of metamorphosis or 

 development of the various types of living beings, or, 

 in other words, of the single structural features which 

 define them. . . . As it is evident that the more 

 comprehensive groups, or those of highest rank, have 



many such examples among the mammalian subdivisions in the 

 remaining portion of his lecturt. 5. Two alternatives are yet open 

 in the explanation of the process of evolution : since generalized 

 types, which combine the characters of higher and lower groups of 

 later periods, must thus be superior to the lower, the lower must 

 (first) be descended from such a generalized form by degradation ; or 

 (second) not descended from it at all, but from some lower contem- 

 poraneous type by advance ; the higher only of the two being de- 

 rived from the first-mentioned. The last I suspect to be a true ex- 

 planation, as it is in accordance with the homologous groups. This 

 law will shorten the demands of paleontologists for time, since, 

 instead of deriving all reptilia, batrachia, etc., from common or- 

 igins, it points to the derivation of higher reptilia of a higher order 

 from higher reptilia of a lower order, lower reptilia of the first from 

 lower reptilia of the second ; finally, the several groups of the low- 

 est or most generalized order of reptilia from a parallel series of 

 the class below, or batrachia, 



