166 LIFE OF 



foremost men of science in every country are either 

 avowed champions of its leading doctrines, or at any rate 

 abstain from opposing them." His prescience has in less 

 than a generation been justified by the discovery of inter- 

 mediate fossil forms of animals too numerous to be here 

 recounted. The break between vertebrate and inver- 

 tebrate animals, between flowering and non-flowering 

 plants, between animal and plant, is now bridged over by 

 discoveries in the life histories of animals and plants 

 which exist to-day. Embryo animals and plants are now 

 known to go through stages which repeat and condense 

 the upward ascent of life ; and they give us information 

 of the greatest value as to lost stages in the path. 

 We can, as it were, see the actual track through which 

 evolution may have proceeded. " Thus," says Professor 

 Huxley, " if the doctrine of evolution had not existed, 

 palaeontologists must have invented it, so irresistibly is it 

 forced upon the mind by the study of the remains of the 

 Tertiary mammalia which have been brought to light since 

 1859;" and again, "so far as the animal world is con- 

 cerned, evolution is no longer a speculation, but a state- 

 ment of historical fact." 



As to the limits of the truth of Darwin's theory, Pro- 

 fessor Huxley, writing on " Evolution in Biology," in 

 " The Encyclopaedia Britannica," says : " How far natural 

 selection suffices for the production of species remains to 

 be seen. Few can doubt that, if not the whole cause, it 

 is a very important factor in that operation ; and that it 

 must play a great part in the sorting out of varieties into 

 those which are transitory, and those which are per- 

 manent. But the causes and conditions of variation 



