334 Professor E. Forbes on the Distribution of 
But the rapid accumulation of paleontological facts gathered within 
the last very few years, and the great additions that have been re- 
cently made towards our knowledge of the Paleeozoic fauna, all 
mainly in accordance with facts known before, have satisfied me that 
the explanation offered above does not sufficiently meet the full 
truth, and that the various theories concerning progression, develop- 
ment, &c., have all originated in the obscure perception and imperfect 
interpretation of the workings of some great law in the distribution 
of organic beings in time. 
It is no longer possible, in the face of paleeontological evidence, to 
hold any of the notions cited. The scale of the first appearance of 
groups of beings of any degree is most clearly not one of organic 
progression. Suitable conditions have been met by the creation of 
suitable types; no type, whether generic and therefore ideally mani- 
fested, or specific and therefore manifested actually and through in- 
dividuals, visibly, being found to be ever repeated in time, when 
the full history of either is made out. This is a great law, and a 
grand result of geological research. Nevertheless, in the relative 
arrangements, so to speak, of generic types in time, there is an indi- 
eation of the working of a general law of another kind, and one which 
seems to me to depend on the manifestation of the relation of Po- 
larity. 
We are accustomed to group all geological epochs under three 
great sections, the Paleozoic or oldest, the Mesozoic or middle, and 
Cainozoic, more commonly termed Tertiary, or newest. If we con- 
sider the faunas and floras of these three great sections, we cannot 
but perceive that there is a far stronger affinity between the Mesozoic 
and Tertiary epochs than between the Mesozoic and Paleozoic. 
This is especially manifest when we regard the details of the distri- 
bution of those preservable forms of animal life, which being inhabi- 
tants of the medium in which sedimentary strata are deposited, are 
most likely to afford an approach towards complete evidence. On 
the other hand, the forms of life that characterize the Paleozoic 
formations, the products of a vast succession of time-periods, have, 
when regarded in their totality, a wonderful agreement and relation- 
ship among themselves. 
For this reason I propose to denominate the sum of the epochs 
after the Patmozoic, by the name of Nrozotrc. 
Now if we regard these two great periods separately, we find that 
the manifestation of generic types during each exhibits striking and 
contrasting phenomena, The maximum development of generic types 
during the Paleozoic period wasduring its earlier epochs ; that during 
the Neozoic period towards its later epochs. And thus, during the 
Paleozoic period, the sum of generic types and concentration of 
characteristic forms is to be observed in Silurian and Devonian 
formations ; during the Neozoic period it is during the Cretaceous, 
Tertiary, and present (itself part of the Tertiary) epochs that we find 
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