390 SECTIONAL TRANSACTIONS.—D. 
islands, that the environmental conditions existing cannot be regarded as 
satisfactory factors which have caused this extraordinary diversity. 
To what then can it be ascribed ? 
(1) Is it due to hybridisation ? 
(2) Were the segregates of a cross between ancestral forms distributed 
over a large insulated area which was subsequently broken up by 
subsidences or upthrusts leading to the present disposition of the 
islands ? 
(3) Is it due to the fact that the natural tendency to vary resident in 
all organisms has been uncontrolled by any selective action ? 
No attempt is made to answer these and other questions. The Galapagos 
problem can only be solved by establishing a biological station on the spot 
where experiments in genetics can be conducted. 
Monday, September 9. 
Discussion on ‘ The species problem’ based on the Presidential Address 
(10.0). 
Prof. E. W. MacBripg, F.R.S. 
Even if he could not agree with everything the President said, the speaker 
recognised that the President had the true zoological point of view. For 
the species problem was the zoological problem ; as Lankester said at the 
meeting of the Association in York in 1906, there was this in common 
between the Church and zoological science, that both had set their hearts 
not on the present but on the distant future. The course of evolution was 
the problem which distinguished zoology from its allied sciences of com- 
parative physiology and histology. Prof. MacBride agreed with the 
President that the theory of natural selection did not account for the evolu- 
tion of all species. In his opinion it accounted for the evolution of no 
species. It was simply a dishonest truism and signified merely that ‘ the 
survivors survived.’ It covertly assumed that small heritable variations in 
all directions were constantly occurring ‘ by chance’ and the chance corre- 
spondence of one of these ‘ random variations ’ with the needs of the environ- 
ment determined the survival of the individual. This, so far as modern 
research went, was simply not true. He thought that the President was 
right in stressing the unbroken passage from biological races to sub-species 
and eventually species. But the President should not be distressed by 
the fact that we could not see within our lifetime the inheritance of 
environmentally produced differences of structure. The ‘ engraining ’ 
of environmental effects was a very slow process. Woltereck examining 
lakes in South Bavaria found no peculiar species of Daphnid Crustacea in 
them, but only peculiar sub-species. These lakes were morainic lakes left 
behind by the recession of the great Alpine glacier of the Ice Age, and could 
not be less than 10,000 years old. 
The President was also worried because he could not see the utility of 
certain ‘ characters.’ Let him remind the President that characters were 
abstraction. What lived and survived was not the character but the animal. 
A character was a peculiarity of growth, and the growth of the animal in all 
its parts was a response to the demands of the environment. Certain 
zoologists finding colour variations in parts of gastropod shells which were 
covered by the mantle and therefore invisible, must be due to chance. 
One of our brilliant younger naturalists had shown that in one gastropod at 
least these colour varieties were correlated with different kinds of food. 
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