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a term embracing “ every influence, whether physical, intellectual, or moral.'’ 
The “ medium,”* he goes on to say, renders the existence of varieties absolutely 
necessary ; for if species did not yield to external circumstances — that is to 
say, if individual forms were unable to bend to external circumstances by 
which they are surrounded, to such an extent as to form varieties — they would 
die out, and the “ species would cease to exist.” 
So great is the influence of the “ medium,” that it gives rise to varieties 
sufficiently marked to cause them to be mistaken for different species. 
M. Decaisne, who is attached to the Museum of the “ Jardin des Plantes” 
(where the author also fills a professorial chair), obtained from the country, 
seeds of a well-marked species of plantain, and sowed them in the garden of 
the Museum. They produced seven forms of the plant, each of which had up 
to that time been regarded as a distinct species. These did not differ on 
trifling points alone, hut in the form and covering of the leaves, the roots, &c. ; 
indeed, so great were the distinctions between them, that he considered the 
error of Linnaeus and his successors quite pardonable when he classed them 
as separate species. Allowed to remain in the same “ medium” (in this case, 
the same soil, temperature, &c.), these varieties became permanent ; trans- 
planted elsewhere, their characteristic features disappeared ; and they came 
to resemble one another so closely that it was easy to distinguish them as 
merely varieties of the same species.f 
But the author is not content to draw his examples from the vegetable 
kingdom ; and where does the reader suppose that he finds his most con- 
vincing evidence in favour of the unity and immutability of species ? 
In the experience of Charles Darwin ; and it is extracted from the very 
work, in which that author seeks to show the probability of the transmuta- 
tion of species. 
Here are the words themselves : — 
“ Mr. Darwin has gone still further. Led by his general studies to occupy 
himself specially with the problem of pigeons, he determined to probe it to 
the bottom. He surrounded himself with all the documents collected before 
his time ; procured all the European races, and those of the English Colonies, 
entered into communication with the chief pigeon-fanciers in London, joined 
two special clubs, and himself tried numerous experiments.” 
“ It was only by seeking to attain the truth by every possible means that he 
felt himself warranted in arriving at a conclusion ; and his conclusion is most 
affirmative, in favour of the unity of species. He considers the Rock-pigeon 
(Columba livia) as the original stock from which all domestic pigeons are 
derived.” .... “ Finally ” (says M. de Quatrefages) “ the author sees 
a proof of the unity of origin in all the races of pigeons, in this fact, that the 
most dissimilar may be crossed and produce mongrels that are indefinitely 
fruitful. This is, indeed, a full and entire confirmation of the preceding 
conclusion, as the reader will understand later on.”J 
# The reader will understand that when we employ this term after the 
author, it bears the construction of “ influences or conditions of existence.” 
t A still more striking example of the power of man to modify species or 
varieties is to be found in the experiments of our esteemed contributor 
Professor Buckman upon the wheat-plant, as described in our first number, 
article “ Corn.” 
X We are intentionally literal in our translation of these passages, as we 
desire to keep as close as possible to the original language of M. de 
Quatrefages, 
