40 ASPECTS OF BIOLOGY AND METHOD OF BIOLOGICAL STUDY. 
lay much stress, for it will admit of explanation by referring it to 
the deficiency of the geological record, and then demanding a 
` lapse of time—of enormous length, it is true—during which the 
necessary modifications would be in progress before the earliest 
phase of which we have any knowledge could have been reached. 
Again, we must not lose sight of the hypothetical nature of i 
those primordial forms in which we regard the -branches of our 
genealogical tree as taking their origin; and while the doctrine — 
of the recapitulation of ancestral forms has much probability, 
and harmonizes with the other aspects of the evolution doctrine 
into a beautifully symmetrical system, it is one for which a suffi- 
cient number of actually observed facts has not yet been adduced : 
to remove it altogether from the region of hypothesis. ‘ 
Even the case of the graptolites already adduced is an illustra- 
tion rather than a proof, for the difficulty of determining the true S 
nature of such obscure fossils is so great that we may be alto- 4 
gether mistaken in our views of their structure and affinities. L 
kaaa aaa a a d ia a a a a a a a a aa 
Par. 
To me, however, one:of the chief difficulties in the way of the 4 
doctrine of evolution, when carried out to the extreme length for 
period of time whose vastness is such that the mind of man is 
utterly incapable of comprehending it. Vast periods, it is true, 
are necessary in order to render the phenomena of evolution pos- 
sible; but the vastness, which the antiquity of life, as shown by- 
‘its remains in the oldest fossiliferous strata, requires us to give 
to these periods, may be even greater than is compatible with 
continuity. oe 
We have no reason to suppose that the reproductive faculty in 
which some of its advocates contend, appears to be the unbroken 4 
continuity of inherited life which it necessarily requires through 4 a 
had continued by inheritance through all the ramifications of 
single genealogical tree down to our own time; the branches 
the tree, it is true, here and there falling away, with the extinction 
: of whole genera and families and tribes, but still some alway 
remaining to carry on the life of the base through a period of time 
