186 LLORAS FER. [SEPTEMBER 
will only grow on or in certain media. From a purely chemical stand- 
point, there is therefore nothing in protoplasmic activity which suggests 
any new element; that bacteria thrive under certain conditions but 
not under others, being dependent on their powers of combination and 
subject to the laws of chemical change, is consequently easily explain- 
able. It may, however, be urged that while it is true that bacteria 
are sometimes influenced by some slight alterations in their environ- 
ment, they are often capable of standing great extremes in other 
directions, and in this respect do not resemble unstable and complex 
chemical compounds ; even this difference, however, does not hold, since 
there are many chemically complex and unstable compounds which 
appear relatively stable under certain conditions while they are equally 
unstable under others. There are, therefore, a set of conditions 
associated with early primitive hfe, which, except for the phenomena 
of fission which Spencer has shown, is, like the other properties of 
early protoplasm, capable of a physical explanation—are all explain- 
able by the laws of chemical change, osmosis, diffusion, etc. 
There are, of course, many fallacies to which one is lable in 
dealing with such a question; thus the extreme minuteness of the 
organisms, and our necessarily imperfect knowledge of their life- 
history and structure make it probable that any present-day explana- 
tion will be incomplete. 
I only wish to note that this resemblance is hkely to be at least 
partially true. That this apparent closeness of connection between 
chemical change and bacterial metabolism may appear to future 
generations less close than it does to us is possible, still the increased 
knowledge of the higher organisms, the relation of food-supply to 
bodily exertion, the recent work on digestion, blood-supply, and tissue 
change, do not lead to a less but a more close chemical analogy; in 
any case the inference, as far as the present time is concerned, is in 
favour of a very close connection between the laws of chemistry and 
physics on the one hand, and the forms of vital activity on the other. 
Now, as far as this inference has weight, it must tell against 
climatic modification in favour of climatic and inter-organismal 
adaptation, masmuch as chemical elements have definite affinities, 
enter into definite combinations in fixed proportions; and as any 
alteration in a compound, however complex, must proceed along 
definite lines, it follows that each form or variety of protoplasm, in so 
far as it 1s chemical in nature, can only grow and keep active by 
being fed by certain foods which it can make use of, and by being 
under certain conditions more or less favourable to its organisation ; 
and when a sufficient number of these favourable conditions are not 
present, the surplus energy of the organism must in time run down, 
and the organism will die because it cannot utilise other conditions. 
At the commencement of this article I endeavoured to emphasise 
the importance of keeping in mind the fundamental distinctions 

