NATURAL SCIENCES OF PHILADELPHIA. 293 



One expression of this inherent metaphysical specific individuality, if the 

 term may be allowed, has been said to be the peculiar traits of the intelli- 

 gence of species, their motions, voices and instincts. But intelligence of all 

 animals is susceptible of impressions, the lower the intelligence the less sus- 

 ceptible, and the more automatic. But as we rise in the scale of animal being 

 this impressibility and capacity for education is undeniably exhibited by the 

 dog, horse and all the well known domesticated companions of man. There 

 can, in view of the capacities of Aves and Mammalia in these respects, be 

 little doubt that all animals are educated by the " logic of events," that their 

 intelligence, impressed by changed circumstances, can accommodate itself 

 more or less to them, and that there is nothing in this part of their being op- 

 posed to the principle of "descent with modification." 



There is another difficulty in the way of accepting metaphysical peculiarity 

 or pi'ogenitiveness as isolating species. It is marked often strongly in races' 

 or varieties, which no one pretends to have had distinct origin. Here like 

 produces like continually, though not persistently, but sufficiently to show 

 that it resides in varieties of common origin. The isolation of allied species 

 in fact depends, we believe, solely on the supremacy of the automatic over 

 the intelligent spirit. When the intelligent rises above the bounds of nature, 

 or the automatic, the mixture or separation of allied species depends merely 

 on circumstances of necessity, determined by that intelligence. 



But the metaphysical "potentiality" loses all basis, if the law of accelera- 

 tion and retardation be true, for in accordance with it, in the fullness of times 

 like does not produce like. 



V. Of Epochal Relations^ or those measuring Geologic Time. 



If it can be shown that groups having the developmental relation above 

 insisted on are cotemporaries, and if it can be shown that this relation is iden- 

 tical in kind with that which we regard as measuring the successions of 

 geologic time, we will be led to doubt the existence of any very great inter- 

 ruptions in the course of this succession throughout geologic time. And if 

 we can show that faunJB so related are more or less characteristic of distinct 

 portions of the earth's surface, at the present time, we will be led to anticipate 

 that cotemporaneous faunae in different regions, during geologic periods, also 

 bore such a relation. If this proposition be true, we are led to the further 

 conclusion, which is at variance with received canons, that identity of faunae 

 proves successional relation in time, instead of^synchronism.* That this will 

 ultimately be demonstrated appears highly probable to the writer, though, as 

 yet, the evidence is but fragmentary. 



If the relations expressed under the terms homology and heterology, taken 

 together with the observations on metamorphosis, render it probable that a 

 number of genera have reached their expression points, or periods of metamor- 

 phosis, at near the same time in geologic history, an important point has 

 been gained. If we can render it probable that a cliange in any organic char- 

 acter has been nearly simultaneous throughout a large extent of specific 

 forms, the change becomes, on the latter account alone, of higher than gene- 

 ric value, but characteristic of such groups as Marsupialia, Olamatores, 

 Acrodonta, Arcifera, Jleterocerca and the like. 



We have here, also, an important element in the estimation of the value of 

 apparent interruptions in the geological history of the life of the globe. These 

 interruptions, it is true, are greater than any such theory as the present can 

 bridge over; yet such a theory, if true, lessens their importance. They are 

 in any case well accounted for on the theory of the existence of periods of 

 elevation, during which the life of a given region is necessarily almost en- 

 tirely lost to us, through lack of means of preservation of their remains. 



*This view was first propouaded by and has since been reaffirmed by Huxley. 



1868,] 



