28 Thomas Henry Huxley 



of plan in the thousands and thousands of divers living 

 constructions, and the modifications of similar ap- 

 paratuses to serve different ends." And so, on the 

 Ratthsfiakc, and in his work in continuation of the 

 Rattlesnake investigations, — which occupied most of his 

 time for a few years after his return to London, — there 

 was gradually growing up in his mind a dim conception 

 of the animal kingdom as a group of creatures, not built 

 on half a dozen or more separate plans or types, each 

 unconnected with the other, but as a varied set of modi- 

 fications of a single type. 



When Darwin set out on the Beagle, unlike Huxley, 

 he was an enthusiastic collecting naturalist. He had 

 wandered from county to county in England adding 

 new specimens to his collections of butterflies and 

 beetles. As the Beagle went round the world visiting 

 remote islands, far from land in the centre of the 

 waters, archipelagoes of islands crowding together, 

 islands hugging the shore of continents, and the great 

 continents of the old and new worlds, he continued to 

 collect and to classify. Gradually the resemblances 

 and differences between the creatures inhabiting differ- 

 ent parts of the earth began to strike him as exhibiting 

 an orderly plan. He saw that under apparently the 

 same conditions of food and temperature and moisture, 

 in different parts of the world the genera and species 

 were different, and that they were most alike in regions 

 between which there was the most recent chance of 

 migrations having taken place. In the quietness of 

 England, while Huxley was on the Rattlesnake, Darwin 

 was .slowly working towards the explanation of all he 

 had seen : towards the conception that animals and 

 plants had spread slowly from common centres, becom- 

 ing more and more different from each other as they 



