160 GEOLOGICAL BIOLOGY. 



expands the Latin phrase of Harvey " omne vivum ex ovo" 

 into " omnum vivum ex vivo" and carries the evolution idea 

 still further in the phrase " omnis cellules cellula." 



The Fact of Evolution Established Beyond Controversy; the 

 Eeal Nature of Evolution to be Learned only by a Study of the 

 History of Organisms. The followers of Cuvier, with their 

 "immutability of species," recognized the principle of " de- 

 velopment " in the sense above defined, but they believed that 

 the metamorphoses, which are called evolution, are the results 

 of independent originating force, or they discarded the belief 

 altogether. The more modern school, represented by the 

 idea of the " mutability of species," fully accepts both devel- 

 opment and evolution as established facts in the order of 

 nature. This principle of evolution is so far-reaching in its 

 application, and so dominates the speculations of our times, 

 that typical illustrations of it as exhibited in the history of 

 organisms are worthy of special study in order that these 

 applications to other things may be correctly made, for only 

 by understanding precisely what evolution is in nature can 

 one apply the term correctly in discussing the philosophical 

 application of it to other things. 



What is an Individual ? When we push the analysis of 

 organic nature farther, we meet the question, What is the in- 

 dividual ? A very superficial consideration of the problem 

 shows us that the organic individual is not merely the sum of 

 the matter constituting the body of the individual at any par- 

 ticular time. The matter of the individual is not made in the 

 course of the growth, but it is only organized. The matter 

 in the case is the food, which before was not a part of the 

 individual. So that it is true to say that an organic indi- 

 vidual develops, but the matter it uses is not in any sense 

 characteristic of the individual, nor is the particular structure 

 of the cells or tissues, for this is common to other individuals, 

 but each individual differs from others in the mode and pur- 

 pose of its activities, and in the results of such activities as 

 expressed in its morphological characters. 



In other words, the organic individual is what it is in each 

 case, not by virtue of the chemical or physical materials of 

 which it is composed, but by virtue of the form, structure, and 



