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duced by man. (2) The existence of barriers either on land or in 
sea will separate between very distinct forms of life ; but where 
these barriers are incomplete or of recent origin the separation of 
species is less marked. The existence of apparent exceptions to 
this rule might be accounted for by former conditions as, e.g., the 
prevalence of extreme cold during the post-pleiocene glacial epoch. 
(3) Again, as highly divergent forms are most likely to survive, 
we should naturally expect to find that the common progenitor 
occupies an intermediate position. Geological discoveries very 
frequently supply these intermediate forms, and so far strengthen 
the theory. (4) Upon Mr. Darwin's supposition, extinct species or 
genera will never reappear. Geology shows that this is actually 
the case. (5) Species in a particular area closely resemble extinct 
species in the same area. (6) The theory is helped by the phe- 
nomena of variation under domestication, and the obvious plasticity 
of their organization which tends to further variation. (7) The 
similarity of embryonic forms in widely separated species and 
genera tells in the same direction. (8) As does also the existence 
of abortive or rudimentary organs. 
Some of the commoner objections to the theory were then 
touched upon, as for example: — (1) The absence of innumerable 
intermediate forms in nature, or in the records of the past. Their 
absence now is explained by the very supposition of the theory; 
their absence in the past by the extreme imperfection of the 
geological record. (2) The impossibility of developing extremely 
perfect organs, as the eye, has been insisted on as fatal. Eut 
examples of these organs can be pointed out in every stage, from 
the most simple to the most complex. (3) The formation on 
modification of instincts, implied by this theory, has been regarded 
as an impossibility. But instincts are modified under domestication, 
and, if it be true that instincts are " inherited habits," they may 
be modified as well as organs. (4) The phenomena connected 
with the fertility and sterility of mongrels and hybrids, though 
very Complex, disclose no essential distinction between a species 
and a variety. 
The lecturer, in conclusion, stated his belief that Mr. Darwin's 
theory must at least receive a provisional acceptance from scientific 
men, as it explained conflicting facts more completely than any 
other view. Possibly Mr. Darwin had not given sufficient weight 
to the modifying power of external conditions, and had laid too 
