Il6 FRANK R. LILLIE. 



composition is heterogeneous. For the rest, exactly the same 

 principles apply as in Fig. 8, except that astral rays are not very 

 numerous in the basophile cap ; this is due to the fact that the 

 section is near the margin of the cap and contains therefore a 

 large proportion of acidophile granules. 



Fig. 9 finally is a transverse section across a spindle lying 

 partly in and parti)'- out of a very dense basophile cap. It is 

 obvious that the spindle area has been invaded on one side by 

 the basophile granules. These are in fact so numerous and are 

 stained so deeply that they almost conceal the chromosomes 

 embedded in them. The concentration of the granules within 

 the spindle area is thus extremely different on the two sides, but 

 on each side it is precisely the same as in the neighboring 

 cytoplasm. 



These cases are typical of a large number in my preparations. 

 It is obvious that there is a great difference in the fatty and acido- 

 phile granules on the one hand and the basophile granules on 

 the other, with reference to their effect on the karyokinetic figure. 

 The former efface any part of the figure which they occupy, the 

 latter are arranged conformably to the lines of the figure. This 

 difference is not conceivably a mere question of size, it is rather 

 a question of specific behavior. The basophile granules behave 

 as though they were within effective range of centers of force to 

 which they are permeable ; the fatty and acidophile granules on 

 the other hand behave as impermeable particles would behave in 

 such a field. 



It is worth while to examine this idea more carefully because 

 the center of force hypothesis alone can render account of the 

 results of these experiments. Theoretically, on a center of force 

 hypothesis the following results might be expected : (l) That 

 the number of radiations from the center would be a factor of 

 the density of aggregation of the more permeable particles ; if the 

 number of permeable particles within the effective area were 

 greatly increased the number of rays should therefore become 

 greater. (2) The number of oriented particles in the same length 

 of any ray should also be a factor of the density of aggregation 

 of the permeable particles. 



We would therefore expect on the center of force hypothesis 



