VALUE OF THE ATTRACTIOX-SPHERE. 325 



among the prime factors of the cell, is reduced to the 

 narrow limit of the centrosome. u Seine Grosse ist an der 

 Grenze des eben sichtbaren, und bleibt haufio- unter dem 

 Durchmesser kleinster Mikro-organismen Zuruck," as 

 Hertwig says (26), while these minute constructions are, as 

 we have seen, not in themselves distinguishable from other 

 cellular granulations (microsomes). It is only their position 

 in relation to the rest of the sphere, which confers upon 

 these particles their peculiar distinction, and it is accordingly 

 not surprising; that within the last few years the opinion 

 has continually gained ground among observers, that it is 

 possible, if not probable, the centrosomes and microsomes 

 may eventually prove to be really of the self-same nature. 

 This view has found its most complete expression in the 

 theory of Watase, who regards (27) the centrosomes as 

 nothing more than accentuated microsomes, or rather cyto- 

 microsomes as he prefers to call them. He consequently 

 denies them the possession of any properties peculiar to 

 themselves. They only exhibit those which might be 

 acquired by any other cyto-microsomes, their actual pecu- 

 liarities arising entirely by virtue of position ; and, thus 

 considered, they may be looked upon as structures lying 

 in the foci of the forces which divide the cell. 



The observations of Heidenhain (8) on the centrosomes 

 in various forms of leucocytes have shown that they may 

 become split up into one, two, three, or four small particles, 

 which in their totality constitute what he terms a Micro- 

 centrum, and his investigations f the oiant cells of the red 

 marrow show a still further multiplication of these central 

 constituents of the sphere. He maintains, moreover, that 

 the centrosomes grow by a process of continual budding, 

 and that in this fact lies the explanation of the curious and 

 habitual difference in size which they exhibit when paired, 

 either during rest or at the apices of the spindle figure, the 

 smaller being regarded by him as simply the younger of the 

 two. Now, the cytosomes which exhibit this singular 

 capacity for growing and dividing, when subjected to the 

 action of stains, appear by no means all alike. Any one who 

 has actually studied centrosomes will have a lively impres- 



