124 THE DAWN OF LIFE 



ductive buds or germs to establish new colonies of the species. 

 Such was the general mode of growth of Eozoon, and we may 

 now consider more in detail some questions as to its gigantic 

 size, its precise mode of nutrition, the arrangement of its 

 parts, its relations to more modern forms, and the effects of 

 its growth in the Laurentian seas. 



With respect to the size of Eozoon, this was rivalled by 

 some succeeding animals of the same humble type in later geo- 

 logical ages ; and, as a whole, foraminiferal animals have been 

 diminishing in size in the lapse of geological time. This is 

 indeed a fact of so frequent occurrence that it may almost be 

 regarded as a law of the introduction of new forms of life, 

 that they assume in their early history gigantic dimensions, 

 and are afterwards continued by less magnificent species. The 

 relations of this to external conditions, in the case of higher 

 animals, are often complex and difficult to understand ; but in 

 organisms so low as Eozoon and its allies, they lie more 

 on the surface. Such creatures may be regarded as the 

 simplest and most ready media for the conversion of vegetable 

 matter into animal tissues, and their functions are almost 

 entirely limited to those of nutrition. Hence it is likely that 

 they will be able to appear in the most gigantic forms under 

 such conditions as afford them the greatest amount of pabulum 

 for the nourishment of their soft parts and for their skeletons. 

 There is reason to believe, for example, that the occurrence, 

 both in the chalk and the deep-sea mud, of immense quanti- 

 ties of the minute bodies known as Coccoliths along with 

 Foraminifera, is not accidental. The Coccoliths appear to be 

 grains of calcareous matter formed in minute plants adapted 

 to a deep-sea habitat ; and these, along with the vegetable 

 and animal debris constantly being derived from the death of 

 the living things at the surface, afford the material both of 

 sarcode and shell. Now if the Laurentian graphite represents 

 an exuberance of vegetable growth in those old seas proper- 



