Juuy 16, 1897]. 
tained. It is, moreover, this becoming per- 
manent, by hereditary acquirement of the 
variation, which constitutes the evolutional 
progress of the series. And the difficulty 
we meet with is that we are assuming that 
natural selection must actually check, or 
even stop that variational activity by means 
of which any change whatever is attained, 
according to the theory of a primitive law 
of heredity. But if we were to grant that 
progress could be attained in this way, and 
allowing the slow rate of the actual process 
by which a variety becomes permanent 
enough to be called a strain or set habit of 
a race, and granting Professor Poulton’s 
demand of the necessary four hundreds of 
millions of years for the process at the 
present rate—granting all this to be pos- 
sible, we have still to reckon with a still 
more important process, the raising of the 
functional importance of the new varietal 
modification to reach a rank of specific, 
generic, family, ordinal, and, before we are 
through with it, class, branch and sub- 
kingdom value in the individual economy. 
The time required for this would be prac- 
tically infinite. Because, with each step in 
advance in taxonomic rank and importance, 
the rigidity of transmission must be sup- 
posed to become greater, and thus the de- 
gree of possible variability diminishingly 
less. This would result, even if we were to 
grant that the change in taxonomic rank of 
the character be a fact. 
But the evidences of paleontology go to 
disprove the very matter of fact. As has 
been already pointed out in another place, 
the degree of differentiation and the classi- 
fication of invertebrates of the first great 
era in which we have definite records of 
organic life are so closely in conformity 
with that which we know of the inverte- 
brates of the same classes now living 
that all the distinctions necessary to be 
considered in an ordinary course of lec- 
tures to a class of students in invertebrate 
SCIENCE. 81 
zoology, to-day, would apply, so far as 
the facts are recorded, to the organisms 
which lived in the earliest period of which 
we have definite record of any living or- 
ganism on the face of the earth (‘ Geologi- 
cal Biology,’ p. 212). This evidence means 
that the same kind of characters, which are 
varietal and specific characters in living or- 
ganisms to-day, were varietal and specific 
characters in the representatives of the same 
classes back in the Cambrian time; thatthe 
same kind of characters which are now gen- 
eric in rank were then generic characters. 
And, so, in the case of family, ordinal and 
class characters we discover no trace of evi- 
dence that characters bearing a particular 
rank in the organic economy now, among 
living beings, did not always bear the same 
relative position among the characters of the 
bodies of their ancestors. 
Attention was called to these facts sev- 
eral years ago and their validity does not 
appear to have been questioned. We ob- 
serve, further, that in Cambrian time the 
differentiations of animals of branch value 
had already taken place, with the exception 
of vertebrates ; and vertebrates appeared in 
the Ordovicean. And in the ease of the 
vertebrates of the Ordovicean (and only a 
single locality for them is as yet known) 
their representatives are distributed by ex- 
perts into three of the five known (i. e., in 
fossil condition) sub-classes of Fishes. 
Fishes, it must be observed, include the 
type of vertebrates which are adjusted 
alone to an aqueous environment, and, 
therefore, we may conclude that, so far as 
the vertebrates of the environment of which 
we have any record for that era are con- 
cerned, they had reached over one-half the 
differentiation of sub-class rank ever at- 
tained by them. 
Lest there should appear to be a mis- 
representation of the opinions against 
which these arguments are directed, quota- 
tion from Darwin’s ‘ Origin of Species’ on 
