1896.] Life Before Fossils. 193 



must have been of very great duration; for the conditions 

 were such as to make evolution a slow process. The habitat 

 of these primeval life forms, the oceanic waters, was of the 

 greatest uniformity, even probably in temperature, and pos- 

 sessed no condition likely to provoke rapid variation. There 

 was abundant space and probably abundant food, particularly 

 in view of the minuteness and slight nutritive demands of 

 these early animals, and the struggle for existence could not 

 have been active. Though there w r ere millions devoured 

 hourly, there were trillions provided for the feast, so that no 

 great tendency towards the preservation of favorable variations 

 would have existed. 



Yet, though the influences which favor evolution were not 

 very actively present, they could not have been quite absent. 

 The innate tendency to vary w T hich all living forms possess 

 now must have existed then, and the advantage possessed by 

 the more highly over the more lowly organized forms could not 

 have been quite wanting. Consequently, development of vary- 

 ing life forms must have gone on at some rate, and animals 

 must in time have appeared much higher in organization than 

 the simple forms from which they emerged. 



And the variations which took place were radical in charac- 

 ter. Variation in the higher recent types of life does not pen- 

 etrate deeply. After ages of change a vertebrate is a vertebrate 

 still. Millions of years of change do not convert a cat into some- 

 thing radically distinct from a cat. But in the primitive period 

 the changes were more profound. Variation went down to the- 

 foundation plan of those simple forms and converted them at 

 once into something else. A degree of variation which now 

 would modify the form of a fish's fin may then have converted! 

 a monad into a new type of animal. Thus primitive evolution, 

 working on forms destitute of any definite organization, may 

 readily have brought into existence a number of highly differ- 

 ent types of life. As the microbe, for instance, may through 

 long variation have given rise to the two organic kingdoms of 

 animals and plants, so the amoeba or other low animal form 

 may have varied into the subkingdoms of mollusca, echinoder- 

 mata, ccelenterata, etc., or rather into simple swimming forms* 

 14 



