i877-J 
and the Evolution Hypothesis. 
525 
species are found still in existence. This would appear to 
indicate that the existing species have been evolved by the 
same law as the extindl ones, which have in reality become 
transformed into the higher type. 
It is probable that many adaptations ascribed to natural 
selection may have been formed by instindl developed by a 
faculty of evolution or expansion, establishing habits which 
have readied on the organisation. In this way it is possible 
to account for the incipient stages of modifications which 
cannot at first have been of any use to their possessors, and 
the difficulties urged by Mr. St. George Mivart on this sub- 
jedl may be thus disposed of. I have not made the nature 
of the developmental agency an element or condition in 
any of the arguments I have hitherto used. I have reserved 
this subjedl for the concluding part of the paper. 
The question arises whether this agency be molecular force 
alone or not ? Because heat accompanies all organic opera- 
tions, it is inferred, by those who hold the mechanical view 
of life, that heat is the sole agent in all processes. To refer 
embryonic changes to the adtion of heat simply because 
they take place only between certain limits of temperature 
is as illogical and as unwarrantable as it would be to con- 
sider the shape of a horse-shoe due to the same cause, for 
no better reason than that the application of a certain 
amount of heat from the furnace is necessary to its forma- 
tion. A quotation in the first part of this paper suggested 
that the mechanical view of life would be demonstrated only 
when all the motions in an organism are shown to be the 
effedls of forces which at other times are inherent in its 
atoms. It could not be expedled that atoms should lose 
their physical properties on becoming component parts of an 
organised strudlure ; moreover, molecules do not at all 
times possess the same power of arranging themselves as 
when they become the building materials of a developing 
embryo. 
It is certain that heat and light play an important part 
in the economy of life ; it is probable that they perform all 
the work ; but there is not sufficient reason for believing 
that they alone effedl the evolution of organisms. There 
are, however, many reasons for believing the contrary. 
We know that no imaginable combination of chemical 
operations, no possible application of heat or light, can pro- 
duce one drop of an organic acid from inorganic materials. 
Prof. Tyndall,* M. Pasteur, and the Rev. W. Ballinger, 
* In a recent le&ure of Professor Tyndall’s, the following remarks occur: — 
“ From the beginning to the end of the inquiry there is not, as you have seen, 
