278 GENERALIZATIONS. 



tion. Although, therefore,, the typical distinctions of plants and 

 animals are not produced by external conditions, such as climate 

 and food, yet these two elements are of great importance both to 

 animals and vegetables, which must adapt themselves to the 

 world surrounding them in order that they may live in it. In 

 the most distant ages, when the sea still covered the whole earth, 

 only aquatic plants and marine animals could have lived. But 

 aquatic life is less perfect than terrestrial life. Aquatic plants 

 and animals now generally possess a lower grade of organization 

 than those of the land ; and, indeed, both the vegetable and the 

 animal kingdoms have their lowest and most primitive forms in 

 the water. That the inferior aquatic forms first appear upon the 

 globe is therefore in accordance with the state of the surface of 

 the earth. As dry land was produced, new conditions of exist- 

 ence were offered ; and these must have prevailed more and more 

 as the dry land increased in extent and in variety of structure, 

 the climatic conditions being at the same time altered by the 

 gradual cooling of the earth's crust and the frequent changes 

 in the distribution of sea and land. Hence, as the development 

 of the solid crust of the earth advanced, its physical constitution 

 became more and more complicated, and the fundamental condi- 

 tions of the development of living organisms became more mul- 

 tifarious. But although, in consequence of these modifications 

 of the crust of the earth a suitable place was furnished for the 

 development of more and more highly organized creatures, the 

 lower ones did not therefore disappear. They are still repre- 

 sented in the existing creation, and have still, as in the earliest 

 periods of the earth's history, a definite purpose to fulfil. The 

 notion that the earlier creations were only the first essays, and 

 1 ' have served merely as preliminary studies for the highest pro- 

 duction, namely Man/' is consequently childish ; for they also 

 were perfect in their kind, inasmuch as they suited the conditions 

 then prevailing on the earth. But why our earth should have 

 had to pass through such a course of development, and could not 

 have come from the hands of the Creator fitted for the reception 

 of the highest and noblest forms of life, is a question that could 

 only be answered if we knew why we do not find here below any 

 stability either for an isolated individual or for the ever moving 

 and advancing intellectual and physical world. 



