204 GRAND STRATEGY OF EVOLUTION 



VII. The Architecture of Animal Life 



Animal structure is exceedingly complex and diffi- 

 cult to visualize without long experience and famil- 

 iarity with it; nevertheless, so far as it is accessible, it 

 affords us the most tangible record of vital achievement 

 and the best measurement of its progress. 



The progress of life, for example, is more convinc- 

 ingly shown in the structure of an amoeba, jelly-fish, 

 worm, crab, fish, mammal, and man, than it is by their 

 actions, methods of living, or in their manifestation of 

 intelligence, because in all living things the basic pur- 

 poses and functions of life are the same, growth and 

 self-preservation. We cannot picture, or measure, 

 naked acts, or purposes, or intelligence. But physical 

 structures may tell us how far acts are constructive, and 

 to what extent purposes have been accomplished; and 

 the ways and means of their accomplishment must 

 always be expressed in terms of structure. 



VIII. Unicellular Growth (Protozoa) 



The simplest form of animal life is a single cell, a 

 tiny speck of cooperating proteids, and other substances. 

 With little apparent distinctions of parts and organs, it 

 performs all the essential acts of animal life, such as 

 moving, feeding, growing, respiring, excreting, repro- 

 ducing, and dying. Now stirred by the passing inci- 

 dents of riotous surroundings; now driven in rhythmic 

 cycles by waxing and waning heat or light, and atomic 

 migrations. Or swirling air, or water, sweep it here 

 and there; bringing the vital agencies of the world to 

 its very doors, or conveying it to the world's commodi- 



