658 GEOLOGY. 



deposits. Perhaps the most important function of the Spermatophytes 

 lay in their superior serviceabihty as food for the higher land animals, 

 by virtue of their seeds, fruits, and foliage. Neither the Thallophytes, 

 Bryophytes, nor Pteridophytes, nor all combined, approach the Sperma- 

 tophytes in food value for the higher types of animal life, and it is doubt- 

 ful whether the higher evolution of the land animals could have taken 

 place without the previous introduction of the seed plants. It will be 

 noted in the historical narratii^e that the great placental group of mam- 

 mals came in and deployed with marvelous rapidity, as geological 

 progress goes, soon after the Spermatophytes became the dominant 

 form of vegetation. 



Plant life terrestrial rather than marine. — It is to be noticed that the 

 chief development of all the great groups of plants took place on the land, 

 or in the land-waters, rather than in the sea. This is preeminently 

 true of the higher t^^pes, and appears also to be true of even the Thallo- 

 phytes, although the number of individual algae and their total mass 

 is very much greater in the sea than on the land and in the land-waters. 

 But the fresh-water algse appear to possess in a higher degree than the 

 marine forms those plastic and germinal characters from which new forms 

 spring, and are probably to be regarded as the parental type. These 

 are facts to be pondered on, since it has been the current opinion of 

 geologists that life arose in the sea and was propagated thence to the 

 land. The alternative view that hfe developed primarily on the land 

 and in the land-waters and migrated to the sea is not, however, without 

 its support in the plant world, as we thus see, and the plant world was 

 the primitive one; the dependent animal world necessarily followed 

 its development. The hypothesis of a terrestrial origin of life throws 

 a very suggestive cross-light on many geological problems, as will be 

 seen later, and it may well be entertained as an alternative working 

 hypothesis until the facts are more fully developed. 



B. Contributions of the Animal Kingdom.^ 



As already noted, animal life is dependent on the decomposition of 



matter organized by green plants, and the conversion of its potential 



energy into active forms. Animals are, therefore, dynamic rather than 



constructive agencies. Nevertheless they transform organic vegetal 



^Reference books: Zittel's Text-book on Paleontology, translated and edited by 

 > Eastman; Williams' Geological Biology; Nicholson's Manual of Paleontology. 



