74 SECTIONAL ADDRESSES. 
dead and the living,’ and between island species, especially in the 
Galapagos, and those of the nearest continental area. It will be remem- 
bered that Darwin’s pocket-book for 1837, referring to this very evidence, 
contains the words, ‘ These facts (especially latter) origin of all my views.’ 
At the side of a page on which the argument on island life is developed, 
Searles Wood had noted—‘ When I wrote this, Mr. Darwin had not 
broached his hypothesis and was not known to be any other than a 
believer in creation. J.S.W. Jr. 1866.’ Darwin’s ‘ Journal’ was first 
published in 1839, the second edition in 1845, but I have not heard of any 
reader except Searles Wood who recognised, before the appearance of the 
Darwin-Wallace Essay and the Origin, that Organic Evolution was an 
irresistible conclusion from the facts recorded by the author. Other 
important argumeats, brought forward in the manuscript, will, I am sure, be 
read with the utmost interest when it appearsin the Linnean Proceedings. 
A curiously interesting event in 1858, the year of the Darwin- Wallace 
Essay, was the appearance of Omphalos, so well described, with the eager 
expectation and bitter disappointment of its author, in Sir Edmund Gosse’s 
Father and Son. It is unnecessary to repeat on this occasion the often 
told and never-to-be-forgotten story of the Jomt Essay and the Linnean 
Society’s celebration of its fiftieth anniversary, when Wallace protested in 
noble and inspiring words against the undue credit which he considered had 
been allotted to him for his share in the discovery of Natural Selection—a 
discovery brought to him, asit was brought to Darwin, by the reading of 
Malthus On Population. 
The effect of the Darwin-Wallace Essay upon Canon Tristram and the 
appearance, a few weeks before the Origin, of his paper on the Ornithology of 
the Sahara, was brought before this Section by Prof. Newton at Manchester 
in 1887, and by the author himself at Nottingham in 1893. It is, 
however, desirable to emphasise its significance afresh in view of recent 
attempts to throw doubt on the value of concealing coloration in desert 
areas. ‘Tristram was led to a belief in Natural Selection when he read 
the Essay in the light of a recent experience of many months in the 
Algerian Sahara, where he had observed that ‘the upper plumage of 
every bird, .. . and also the fur of all the small mammals, and the 
skin of all the Snakes and Lizards, is of one uniform isabelline or sand 
colour,’ and had come to realise the absolute necessity for the vast majority 
of the species to be thus concealed upon the uniform surface of the desert. 
Precisely the same necessity had been recognised in South Africa nearly 
half a century earlier by Burchell, when he observed the protective 
resemblance of a Mesembryanthemum and a grasshopper to pebbles, and 
the defensive value of thorns and acrid secretions in a bare dry country 
‘ where every juicy vegetable would soon be eaten up by the wild animals.’ 
Burchell’s mention of plants with an ‘ acrid or poisonous juice’ suggests 
the meaning of the conspicuousness of the relatively few black, slow- 
moving insects which have been thought to throw doubt upon the whole 
theory of protective coloration in the desert. The problem is complex 
and the struggle for existence is waged in many ways, important among 
them being the physiological adaptations by which the imperative need 
for moisture is satisfied—a subject on which much light has been thrown 
by P. A. Buxton. 
