334 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
immutability of species, was the basis of life. As it happened, there 
were two reasons why Lamarck’s ideas were unacceptable. The first 
was that he undertook no analysis to provide evidence for his notion 
of evolution: it flashed across his mind, and he assumed its truth 
without taking the trouble to prove it. Secondly, he attempted to give 
an explanation of the causes of evolution which, unfortunately, raised 
opposition to the acceptance of the concept of evolution itself. He 
supposed that as a result of new needs experienced by the animal, its 
“inner feelings” or subconscious activities produced new organs which 
satisfied those needs. Not only was such a supposition unacceptable 
for the solution of the preblem of the origin of species of animals, 
but it was totally inapplicable to plants. On the other hand, Lamarck 
elaborated a view which for a long time was accepted but which is 
now known to be without foundation, namely that the effects of use 
and disuse were transmitted by inheritance. There for a time the 
matter rested. 
THE FACT OF EVOLUTION 
When Darwin started on the voyage of the Beagle in 1831, he had 
no reason to doubt the immutability of species. The speculations of 
his grandfather Erasmus counted for nothing with him, because they 
were not supported by evidence. Those of Lamarck on the causes of 
evolution had the additional demerit of bringing the subject into 
disrepute by their fanciful nature. It must be added that in Lyell’s 
“Principles of Geology,” to which Darwin owed so much because of 
the general background of uniformitarianism in place of catastro- 
phism that it advocated, the possibility of evolution was firmly rejected. 
Three sets of observations started Darwin’s revolt against the im- 
mutability of species. The first was occasioned by his studies of the 
fauna of the Galapagos Islands, where he found that species of 
finches differed slightly from island to island, while showing gen- 
eral resemblances not only to each other but to the finches on the 
adjacent mainland of South America. If these species had been 
separately created, why should there have been such a prodigal expend- 
iture of “creation” just there; why should geographical propinquity 
have caused these “creations” to resemble each other so closely; why, 
in spite of the similarity in physical conditions between the islands 
of the Galdpagos Archipelago and the Cape Verde Islands, are their 
faunas totally different, the former resembling that of South America 
while the fauna of the latter resembles that of Africa ? 
The second set of observations related to the fact that as he traveled 
over South America he noticed that the species occupying a particular 
niche in some regions were replaced in neighboring regions by other 
species that were different, yet closely similar. Why are the rabbitlike 
animals on the savannahs of La Plata built on the plan of the peculiar 
