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been here tacitly assumed which ought to be demonstrated ; namely, that there 
is no species distinguished from another species by the differentia of con- 
sistent reproduction, varying only within a fixed limit. Now this I contend 
Mr. Darwin and Mr. Warington have not proved, and never will. 
Dr. J. H. Gladstone. — While sitting at the other end of the room I have 
been thinking of two functions of this Society — two functions it is supposed 
to discharge — namely, the slaying of giants and the laying of ghosts. By the 
first I mean, that from the border-land of knowledge and no knowledge, huge 
theories and hypotheses stalk forth, which frighten many mortals ; and we 
are disposed to go and fight them. Then sometimes we hear that from a 
suspicious quarter there has risen something very “uncanny;” and our wisdom 
in such a case is to take a candle and walk up and try to put the candle 
through the ghost’s body, when we generally find the ghost to be something 
very innocent after all. If we run away from the ghost, the ghost will haunt 
us, and we deserve it. Now, there is this huge, gigantic and majestic hypo- 
thesis of Darwin, and several attempts have been made to slay this giant. 
Mr. Mitchell tried it in his first Address ; then we have had various questions 
asked by Mr. Reddie on former occasions, and again to-night ; and since then 
it has been defended ; and I think now the battle may go on for some time. 
Then there are various ghost notions about it : some say it is rather infidel ; 
and there are other ideas about it ; but let us look these suspicions in the 
face. As to the question itself, it is not to be expected, in a short speech at 
this late hour, that I can go into it in half its details ; but I have little doubt 
that if Mr. Darwin had put forth his work as “ The Origin of Varieties,” and 
had insisted that they arose from natural selection, it would have been ac- 
cepted as an explanation of the origin of varieties by nearly all naturalists, 
and I do not suppose the question would have come before us here. (Hear, hear.) 
It appears to me so evidently true that there is this struggle for existence, 
that there are these modifications taking place from generation to generation, 
and so true that any modification which is more adapted to the circumstances 
in which an animal lives must give it a better chance of propagation, that 
I think there would be no hesitation in accepting natural selection as a vera 
causa. The difficulty springs up when Darwin extends this, and endeavours 
to push the theory beyond these limits (hear, hear); and then comes the ques- 
tion, whether species exist in nature originally, or are varieties carried to such 
an extent that they become permanent ? That is the question,— a serious one, 
and difficult to answer. On the one hand, do we find any of these limits of 
which Captain Fishbourne has spoken § I do not think we can fix the limits 
of the power of artificial or natural selection ; and, on the other hand, we do 
find something like the actual existence of species in nature that is to say, 
there are allied creatures which are so far apart that they cannot be brought 
together to reproduce any intermediate creature, or if they have any progeny 
it is not fertile. But then, again, as to this question of hybridity, we 
want to be certain about that ; and I think, as experiments can be easily 
carried on with reference to plants, it will be a fruitful source of inquiry 
to find the real phenomena. The whole question turns on this, whether 
