EVIDENCE PROVING THE STATEMENT OF THE CASE 81 



such a particle exists. 1 Now, it may well be asked, why 

 after all should so great importance be attached to this 

 observation ? To this it may be replied that, in the 

 first place, it is of importance, because it shows con- 

 clusively that the whole cell is not of a uniform nature, 

 since there is this one point within the cell that exerts 

 a special attraction upon the rest of the cell-substance ; 

 and, indeed, on this account the particle has come to be 

 termed the l attraction particle.' ~ And in the second 

 place, because of the apparent universality of the 

 occurrence of such a particle. And, thirdly, because 

 of the fact that one of the most important phenomena 

 exhibited by the cell hinges upon the behaviour of this 

 particle ; for it is found that before a cell or its 

 nucleus divides, 3 this minute attraction particle begins 

 by itself dividing, and is, in fact, more commonly 

 met with double than single. Nor is it until the two 

 particles thus produced have evolved, either from them- 

 selves or from the substance of the protoplasm or 

 nucleus, a system of communicating fibres, the so-called 

 achromatic spindle, that those changes in the nucleus 

 and protoplasm take place which produce the division 

 and multiplication of the cell. This attraction particle, 41 

 which is also called the central particle or centrosome, has 

 absorbed so great an interest that, short as is its history, 



1 The italics are ours. 2 The italics are ours. 



3 A cell generally multiplies by dividing itself into two cells, these 

 again into four, these four into eight, and so on : thus cell multipli- 

 cation tends to be in geometrical ratio. 



4 Since this was written further investigation leads to a doubt if 

 this particle is a centre of attraction, but better expressed, it is a 

 condensation or focal point of convergent activity. Either view suits 

 the argument we are dealing with. If this particle does not 

 " initiate and direct" it is intimately associated with such reactions. 



G 



