XIV 



PRESIDKNTIAI. AOIJRES.S 



and importance. This constituent is known as "nuclein"or 

 -chromatin," the lattername being given to it on acco.mt of 

 Its takmg a very deep stain when subjected to staining reagents- 

 The nuucleus not only plays a most important part in the life o^ 

 the cell, but it is that portion of the cell which passes from one 

 generation to another, and in ihis process the chromatin is an 

 active agent. In cell subdivision one-half of it becomes appor- 

 tioned to each of the resulting cells, and it is the medium of 

 the momentous phenomenon of heredity. Besides, the nucleus 

 microscopists have within late years detected in the cell and 

 lying near the nucleus, another small body so minute that ii was 

 overlooked until the efficiency of modern instruments disclosed 

 It. This body, which has been called the - centrosone," apoears 

 to exercise a controlling influence upon the vital phenomena 

 for around it the protoplasmic granules are found to be arranged 

 in rays, as if the lines of force radiated from it. This centro- 

 some generally soon divides into two, and is found reduplicated 

 thus presenting the appearance of two minute stars. The precise 

 function of this body and the nature of its action are at present 

 not understood, but in cell division it appears to be the mechan- 

 ism which controls the process and regulates the apportionment 

 of the chromatin between the resulting new cells. It will now 

 be at once realised how completely the cell theory has been 

 modified since the days when it was usual to talk about proto- 

 plasm as a homogeneous chemical compound, bavin- for its 

 attribute that property of being alive. To look at the" delicate 

 framework of fibres, studded with granules and filled with clear 

 liquid, the complicated nucleus, with its network, and chromatin 

 threads, and nucleolus, and the strange rayed body known as the 

 centrosome lying near it, is to prepare the mind for th5 

 recent enunciation of the cell theory, which is so unlike the old 

 doctrine that nothing but the words remain, and they remain 

 only because without creating any particular confusion they have 

 acquired a new signification. The cell theory may now be con- 

 cisely stated thus : Just as the steam engine is a machine for 

 the production of motion, or the dynamo is a machine for the 

 production of electricity, so the cell is an infinitely subtle and 

 delicate machine, the resultant of whose working is life. This 

 IS a novel and startling deduction, but so consonant with all the 

 observed phenomena and with the structure of the cell that it ' 

 becomes a far more efficient hypothesis than any which have 

 preceded it. So completely have the old views under-one 

 modification, that it has even been questioned lately that" the 



