The Organism and Its Cells 153 



rather than explicitly, lias brought it to pass that many 

 biologists seem to do most of their scientific thinking in 

 terms of cells. The multiform activities of "cell-life," as 

 a common expression has it, appear to be the final thought- 

 goal of such biologists. But the theory is not by any means 

 allowed so broad a scope by all biologists. This finds illus- 

 tration in the article on the theory furnished to the Dic- 

 tionary of Philosophy and Psychology by C. Lloyd Morgan 

 and K. S. (ioodrich. As understood by these authorities, 

 the theory is, "The doctrine that all organisms are composed 

 either of individual cells (unicellular organisms) or of a 

 compound aggregate of cells (the higher plants and animals) 

 with certain cell-products ; and that every cell, no matter 

 how differentiated in structure or function, is derived from 

 a preceding cell." 7 



A few good authorities, for example, Driesch, even go so 

 far in restricting the cell-theory to this aspect of it, and in 

 standing so confidently on its factual nature as to deny 

 that there really is now a cell-theory at all. The cellular 

 composition of all organisms (the unicellulars of course 

 exceptcd) is, he says, "a simple fact of observation, and I 

 therefore cannot agree with the common habit of giving to 

 this plain fact the title of cell-theory. There is nothing 

 theoretical in it." The examination of definitions has 

 gone far enough to bring out several points of prime moment 

 for our enterprise: The cell-theory has been in the past, 

 and still is, understood quite differently by different biolo- 

 gists. In the narrower signification given it by such au- 

 thorities as Morgan and Goodrich, it is held to the strict 

 bounds of a generalization of observations on the minuter 

 make-up of both adult and all developmental stages of plants 

 and animals. Such observations, vast in range and num- 

 ber, have thus far found no exception to the rule that each 

 plant and animal body can be resolved into very small units 

 and products thereof, all the units in each organism being 



