VALUE OF THE ATTRACTION-SPHERE. 157 



can exist quite separate from one another, even during rest, 

 it would be well to find some term to comprehend all these 

 structurally co-related parts wherever they may be situated 

 in the cell. 



In the following pages I have employed the term 

 "Attraction-sphere" in this sense, shortly, " Sphere," reserv- 

 ing " Archoplasm " for the outer granular mass to which it 

 was originally applied and " Centrosome " for the inner 

 oranule. 



Whether, with van Beneden, we are to regard the 

 spheres as organs of the cell depends a good deal upon 

 what is meant by the term organ. In its original concep- 

 tion the word has a physiological significance, and in this 

 sense the purposive nature of any structure constitutes its 

 claim to be regarded as an organ. Consequently both the 

 nucleus, cytoplasm, and all other structures functional in the 

 maintenance of the cell, fall into the category of organs, 

 the spheres with their very definite functions among them. 

 That they are not so regarded by many histologists is 

 nevertheless a fact ; but this tardiness in the acceptance of 

 van Beneden's views has really nothing to do with indefinite 

 terminology arising from certain considerations respecting 

 the origin of the spheres of quite a different nature. 



It has become a biological postulate, engrained by the 

 invariable nature of the evidence on which it rests, that 

 a cell in its origin is possessed of a nucleus and cytoplasm, 

 if nothing else. And it is equally certain that Virchow's 

 aphorism, " omnis cellula e cellula" could be extended down 

 to the origin of the cytoplasm from pre-existing cytoplasm, 

 and the nucleus from pre-existing nuclei of previous genera- 

 tions. But this simple duality of structure, with which cells 

 often start in life, may, and very generally does, give place 

 to a greater complexity of parts, through the development 

 of accessory structures, of which some Nebenkerns form 

 typical examples. Whatever be the function of these 

 bodies (and in many cases it is not known), they are 

 often plainly derived, by direct metamorphosis, from either 

 the nuclear or cytoplasmic substance. They do not 

 come in with the prime constituents at the outset, but are 



