OA' THE NATURE OF CELL-ORGANIZATION. 99 



Take chromosomes of the nucleus, for example. In some cells 

 the physiological units of the chromosome arrange themselves 

 in a series of short rods — chromatomeres — at a certain period 

 of their existence, while in others they arrange themselves in 

 a series of elongated filaments at the corresponding period. 

 What, therefore, we see in the grouping of micro-organisms 

 such as bacteria, exactly applies to those uifits which form the 

 chromosomes. As De Bary 1 says of bacteria, so we may say 

 here, that it is precisely in the phenomena of grouping that 

 specific peculiarities of conformation of such physiological 

 units best display themselves, being collected together, as it 

 were, in large quantity. These groupings are forms of vegeta- 

 tive development, grozvth-forms of the minute organism which 

 constitutes the physiological unit of the chromosome. 



The growth-forms of the physiological unit forming the 

 cytoplasm of the cell are equally characteristic, as is plainly 

 shown in the reticular, striated, or fibrillar arrangements of 

 the cytoplasm in different kinds of cells. 



V. 



To re-state the problem, then, we may say that there 

 exist two easily recognizable elements in every cell, viz,, 

 (a) the nucleus, or more strictly the chromosome, and (d) 

 the cytoplasm. 



It has been conclusively settled by a number of investigators 

 that the presence of both is essential for the continued 

 manifestation of life activity in a given cell. A piece of 

 cytoplasm or nucleus may continue to maintain a certain activity 

 after it has been detached from the cell, but it perishes, sooner 

 or later, if left alone by itself. 



So much is certain, but how and why each is essential to the 

 other are quite other questions, and have received different 

 answers from different investigators. Some claim that the 

 nucleus influences the cytoplasm by some dynamical action ; 

 others hold that some invisible living particles of the nuclear 

 matter diffuse through the nuclear membrane, and become 

 converted into the substance of the cytoplasm ; while still 



1 De T5ary : Lectures on Bacteria, Oxford. 1S87. 



