The Organism and Its Cells 151 



sense, by the theory of cells we understand whatever may 

 be inferred from this proposition with respect to the powers 

 from which these phenomena result." ^ 



Two meanings, a broader and a narrower, are thus ex- 

 pressly indicated ; and the permissive phrase "whatever may 

 be inferred" attached to the more restricted one, points a 

 way to diversification of interpreting it that was sure to be 

 followed. 



In view of the comprehensiveness of the theory as thus 

 initially conceived, it is surprising to find Virchow, one of the 

 earliest and most distinguished promoters of it, speaking 

 of it as pertaining to the mode of origin of cells. "This 

 description of the first development of cells out of free 

 blastema, according to which the nucleus was regarded as 

 preceding the formation of the cell, and playing the part of 

 a real cell- former (cytoblast), is the one which is usually 

 conciseU' designated by the name cell-theory (more ac- 

 curately theory of free-cell-formation)." ^ 



O. Hertwig's statement of the theory is as follows : "Plants 

 and animals, so dissimilar in external appearance, agree in 

 the foundation of their anatomical structure ; for both are 

 composed of similar elementary units mostly visible by the 

 aid of the microscope onl3^ According to an old theory, 

 now abandoned, these units are called cells, so that the doc- 

 trine that animals and plants consist in a similar way of 

 such smallest particles is designated the cell-theory." ^ 



But Hertwig's treatment of the cell in his earlier volume 

 Die Zelle, and in his later more comprehensive work, 

 Allgemeine BioJogie, (4th ed.), surely adds much to the 

 theor}' that is not hinted at in this brief definition. 



The characterization of the theory by E. B. Wilson more 

 adequately expresses its scope as practically understood and 

 used by many recent biologists, including Hertwig himself. 

 "In its broader outlines," writes Wilson, "the nature of this 

 organization is now accurately determined; and the *cell- 



