Organized Beings in Time. — 835 
the maximum development of peculiar generic types (or ideas). On 
the other hand, during the closing epochs of the Paleozoic and the 
commencing epoch of the Neozoic period there was a poverty in the 
production of generic ideas, with few exceptions the species of the 
epochs in question being members of genera that form constituents 
in the assemblage, accumulated during the epochs of maximum of 
generic types or ideas. 
The following table may render my meaning more evident :— 
Present and Tertiary epochs | Epoch of maximum development 
Neozoic }Cretaceous epochs of Neozple Generig types, 
period. es epochs 2...) . » Intermediate, 
Triassic epochs Epochs of poverty of production 
Permian epochs of Generic types in Time. 
Paleozoic }Carboniferous epochs . . . Intermediate. 
period. Devonian epochs Epoch of maximum development 
Silurian epochs of Paleozoic Generic types. 
Before the Silurian and after the commencement of the present, 
no special creations of generic types have as yet been shown to be 
manifested. In the system of life of which all known creatures 
living or extinct as yet described, so far as our knowledge extends— 
and there is a consistency in its co-ordination that suggests the 
probability of our being acquainted with its extremes—the creation 
of the fauna and flora of the oldest. Palzeozoic epoch would seem to 
be the primordial, and the appearance of Man the closing biological 
events. 
When the assemblage of characteristic Neozoic groups or genera 
is contrasted with that of the Paleozoic, there’ we find that the 
concentration of a maximum development of generic types towards 
the earlier stages of the one and the later of the other great period, 
includes something more than a mere numerical profusion of generic 
ideas. The two great manifestations of creative intensity are in 
opposition, or contrast, and respectively snbstitute each other ; 
groups that are parallel within their sub-kingdoms or classes taking 
the place of each other, and playing a corresponding part in the 
economy of nature. This replacement does not depend on the sub- 
stitution of a group of higher organization during the latter epoch, 
for one of lower during the former. Where there is such a substi- 
tution it must be regarded as an accident ; for the rule is not general, 
nor can it be held good except for a few instances. 
A few leading examples of the substitution of group for group 
during the contrasting epochs are cited in the following table, and will 
illustrate this point better than a mere abstract statement. 
NeEozoic. PaL#ozoic. 
Cycloid and Ctenoid Tubes . Ganoid and Placoid Tubes. 
Malacostracous Crustacea . . Entomostracous Crustacea. 
Dibranchiate Cephalopoda . . Tetrabranchiate Cephalopoda. 
