ox thb: nature of CELL-ORGANIZATIOX. 87 



use it as a working theory in the explanation of cellular 

 phenomena such as I have already indicated. For it is possible 

 that the law followed by the ccll-aggrcgatc in the course of its 

 development, may not have been followed in the formation of 

 the individual cell. 



It is perfectly conceivable that the process by which the cell 

 was first formed may have been due to causes of special 

 character, while the conversion of the cell thus formed, into an 

 organism of higher complexity, may have been due to causes 

 entirely different from those that operated in the production of 

 the nucleated cell. 



There is no necessary reason to conclude, as has been done 

 by several naturalists, that because the complex organism 

 develops by a process of differentiation of the homogeneous 

 germ, the duplex structure of the cellular units which compose 

 the organism, must have also had a parallel course of develop- 

 ment from its antecedent germ. 



It is this point that I wish to discuss more in detail in the 



following. 



II. 



The parts of a living organism commonly termed its organs 

 may be studied from three points of view : — 



1. How far are these parts adapted, by their form and 

 structure, to perform their physiological work } This mode of 

 studying the organs belongs to physiology. 



2. Where and how do they arise in a given organism t This 

 field of study is a branch of morphology. 



3. If the morphological study of the organ be extended 

 through organisms of different grades of complexity, it may 

 enable us to infer the probable steps through which the given 

 organ may have passed in the course of its phylogenetic history. 



When these three modes of study as pursued by naturalists 

 at the present day, are applied to the study of organs of an 

 individual cell, it resolves itself into three problems : — 



I. How far are nucleus and cytoplasm adapted by their form 

 and structure, to perform their physiological work in a given 

 cell? 



