TRANSACTIONS OF THE SECTIONS. 11] 
_ The species may be characterized as follows:—Polynema natans, n. 8.: male, black ; 
female, black ; legs, eight basal segments of antennz, posterior part of thorax, and 
peduncle ferruginous. 
The second new species is more peculiar, and must form a new genus. It occurred 
with the first, but was much rarer, only six specimens having been met with, all of 
which were females, Perhaps the males are not aquatic in their habits. In this 
case, however, it was the hind legs which were used for swimming, although they 
possessed no fringe or other apparent indication to adapt them to their new function. 
On the Influence of Changes in the Conditions of Existence in Modifying 
Species and Varieties. By the Rev. W. N. Mouesworra, M.A., Rochdale. 
The author of this paper commenced by giving a brief sketch of the main features 
of Darwin’s theory of the origin of species, in order that its salient points might be 
kept in view by the audience during the reading of the paper. He then proceeded 
to point out that the theory thus outlined was not a mere wanton attack on beliefs 
and feelings which every one was bound to respect, but was intended to supply a 
scientific desideratum ; and that, whether proved or disproved, it was calculated to 
advance our knowledge of the sciences to which it related. He wished it, however, 
clearly to be understood that his approval was limited to the theory of the origin 
of species, and not to the conjectures respecting the origin of organic life which 
are put forward at the close of the book—conjectures which, he submitted, it was 
impossible either to prove or disprove, or even to adduce any facts bearing on them, 
and which therefore cannot lead to any scientific results. 
After considering some objections which had been made against the Darwinian 
theory, the author of the paper proceeded as follows :— 
And how is it that, with all their differences, they all possess so many characters 
incommon? Howisit that the line of demarcation which separates them is often 
so faintly traced that we lose sight of italtogether ? These are the questions which 
Mr. Darwin raises, and to which he has given an answer, which, whether true or 
false, is certainly highly ingenious and original, and supported by a large array of 
facts. Whether his theory is true or not is a matter on which I express no opinion ; 
but that a necessity exists for a theory on the subject to which it relates is, | would 
submit, a matter that admits of no doubt. 
There is another of Agassiz’s objections that seems to me better founded than 
that with which I have just been dealing. He says, “The assertion of Darwin, 
which has crept into the title of his work, is that favoured races are preserved, 
while all his facts go to substantiate the assertion that favoured individuals have a 
better chance in the struggle for life than others.” In this passage Agassiz seems 
to me to have pointed out the respect in which Darwin’s theory is defective and 
stands in need of further elaboration. I contend that he has not paid sufficient 
attention to a very manifest and important principle, which has probably played as 
large a part in the origination of species and varieties as either the struggle for 
existence or natural selection. I mean the change which is continually going on 
in the conditions of existence, and which, by affecting a great number of individuals 
in the same manner, tend to produce similar modifications in all the beings who 
are surrounded by them. In employing the term “ conditions of existence,” | mean 
to imply the totality of the circumstances by which the organized being is sur- 
rounded—the air, the climate, the soil, the vegetation, and the animals which inhabit 
the same area, including those of its own species. All these are, if we look at the 
matter rightly, conditions of its existence, inasmuch as all of them exercise a more 
or less powerful influence on it, causing it to be other than it would be if they 
were absent or different from what they are. The thing to which I desire to draw 
particular attention is the change which is always going on in these conditions of 
existence, owing to their mutual actions and reactions. For instance, the very 
constitution of the atmosphere is to a certain extent altered by every organized 
being, as well as by the inorganic matter with which it is continually entering into 
new combinations. If any one should suppose that the changes thus produced 
must be quite inappreciable even though carried on through millions of generations, 
let him reflect for a moment on the enormous quantity of former constituents of the 
