104 THE DATA OF BIOLOGY. 



that the life is groat in proportion as the correspondence is 

 great. For if the lengthened existence of a tree he looked 

 upon as tantamount to a considerable amount of life; then 

 it must be admitted that its lengthened display of corre 

 spondence is tantamount to a considerable amount of corre 

 spondence. If, otherwise, it be held that notwithstanding its 

 much shorter existence, a dog must rank above a tortoise in 

 degree of life because of its superior activity; then it is 

 implied that its life is higher because its simultaneous and 

 successive changes are more complex and more rapid be 

 cause the correspondence is greater. And since we regard 

 as the highest life that which, like our own, shows great 

 complexity in the correspondences, great rapidity in the suc 

 cession of them, and great length in the series of them; the 

 equivalence between degree of life and degree of correspond 

 ence is unquestionable. 



33. In further elucidation of this general truth, and 

 especially in explanation of the irregularities just referred to, 

 it must be pointed out that as the life becomes higher the 

 environment itself becomes more complex. Though, literally, 

 the environment means all surrounding space with the co 

 existences and sequences contained in it : yet, practically, it 

 often means but a small part of this. The environment of 

 an entozoon can scarcely be said to extend beyond the body 

 of the animal in which the entozoon lives. That of a fresh 

 water alga is virtually limited to the ditch inhabited by the 

 alga. And, understanding the term in this restricted sense, 

 we shall see that the superior organisms inhabit the more 

 complicated environments. 



Thus, contrasted with the life found on land, the lower 

 life is that found in the sea; and it has the simpler environ 

 ment. Marine creatures are affected by fewer co-existences 

 and sequences than terrestrial ones. Being very nearly of 

 the same specific gravity as the surrounding medium, they 

 have to contend with less various mechanical actions. 



