1 86 MARINE BIOLOGICAL LABORATORY. 



most carefully studied by several investigators. At first 

 the two daughter spheres he in close opposition, later 

 they separate more and more widely. As each sphere 

 has a system of radiating filaments, there is formed a 

 little spindle (Fig. 6, S) where they come into contact. 

 This spindle lies outside of the nucleus, and has nothing 

 to do with the larger one which has been described 

 already. The daughter archoplasmic spheres migrate 

 further apart, and finally settle themselves on the oppo- 

 site sides of the nucleus. Their effect on the latter is 

 soon seen. That surface of the nucleus upon which 

 the archoplasm rests soon shows signs of flattening, as 

 was shown in Fig. 3. This polar flattening of the 

 nucleus has been interpreted as due to the pressure 

 exerted by the growing archoplasmic filaments. The 

 growth of the filaments continues, and the effects it 

 produces upon the nucleus, in the arrangement and 

 distribution of the chromosomes have already been de- 

 scribed. Compare in this connection the series of stages 

 shown in Figs. 3, 4, 5, and i. 



The above is a sketch of the mechanics involved in 

 the distribution of the nuclear substance in the dividing 

 cell. The history of the formation of the spindle has 

 been briefly given, and the mode of its activity has been 

 suggested. The spindle, however, plays only a part in 

 the production of the caryokinetic phenomena. The 

 whole behavior of the chromosomes preparatory to di- 

 vision, such as the transformation from a resting con- 

 dition to a coil stage, followed by the longitudinal 

 splitting of each filament, — phenomena which take 

 place independently of the influence of the spindle, — 

 has received no consideration, and, so far as I can see, 



