﻿270 T. Davidson — What is a Braqhioxjod ? 



The imperfection (one due, I believe, to our slight acquaintance 

 with the subject) in the geological record cannot in many cases be 

 doubted, but we have no right to make capital out of iinknown data. 

 We must therefore deal with facts as we find them, and see how far 

 they will bear upon the subject under examination. It may be quite 

 true, that strata at great distances cannot be positively asserted to be 

 strictly speaking absolutely contemporaneous, although they may 

 contain the same animals. 



Prof. Huxley has stated that for anything that Geology and Palae- 

 ontology are able to show to the contrary, a Devonian Flora in the 

 British Islands may have been contemporaneous with a Carbonifer- 

 ous Plora and Fauna in Africa; but as we have no certainty that 

 such has been the case, it cannot be adduced in support of the theory 

 under notice. It is likewise very probable that some species may 

 have migrated from the sea-bottom on which they originally lived 

 to some more favourable locality, and have become to some extent 

 modified. No one can seriously doubt that life has continued to be 

 represented under one form or another ever since it was first brought 

 into existence, and I consequently cannot agree with M. Deslia3'es 

 and others who believe in a total extinction of the animal creation 

 at certain specified periods. We are also aware that, taking, for 

 instance, the rocks of the Carboniferous period, in almost every 

 locality in Europe, Spitzbergen, Newfoundland, America, India, or 

 Australia, there are present a few species common to all, in addition 

 to a number that are special to the locality. Thus, for example, as 

 I have shown elsewhere, Spirifer lineatus is one of those persistent 

 forms, but with different proportions according to the locality, caused, 

 no doubt, from the sea-bottom being more or less favourable to its 

 development. It is consequently very large in the Punjab, of mo- 

 derate dimensions in Europe, and considerably dwarfed in Nova 

 Scotia. Still the species remain essentially the same.^ 



Notwithstanding the theoretical doctrine that has been promulgated 

 with respect to the origin of species, we are still and shall probably 

 for ever remain in ' the dark, or within the region of suppositions, 

 with respect to so important a question. In his admirable address 

 to the Belfast Meeting of the British Association, Tyndall observes : 

 " If you ask me whether there exists the least evidence to prove 

 that any form of life can be developed out of matter, without demon- 

 strable antecedent life, my reply is that evidence considered perfectly 

 conclusive by many has been adduced ; and that were some of us 

 who have pondered this question to follow a very common example, 

 and accept testimony because it falls in with our belief, we also 

 should eagerly close with the evidence referred to. But there is in 

 the true man of science a wish stronger than the wish to have his 

 beliefs upheld; namely, the wish to have them true. And this 



1 It has been observed by Robert MacAndrew tbat although the size attained by 

 Molhisca (and no doiibt by other animals) may be influenced by various conditions ia 

 different localities, as a general rule each species attains its greatest size, as well as 

 its greatest number, in the latitudes best siiited to its general development ; and 

 that whether a species be Arctic, Boreal, Celtic, or Lusitianian, it will grow largest in 

 the reji'lon to which it belongs. 



