108 PROCEEDINGS OF THE AMERICAN ACADEMY. 



mosomes remain clustered together in one place, and finally break up 

 into granules ; and that the spindle fibres are converted into a net- 

 work. While we agree with the main point implied in this description, 

 — viz., that the chromosomes do not separate into two groups repre- 

 sentative of two daughter nuclei, — our observations lead us to think 

 that the nuclear matter does not pass through a true reticular stage. 

 For the chromosomes retain more or less distinctly their individuality, 

 and the spindle fibres do not seem to take on the reticulate condition, 

 but rather, to become confluent into a smaller number of strands. 

 Whatever may be the method of its formation, however, the spindle 

 and its chromosomes present almost exactly the same conditions 

 immediately after the elimination of the interzonal body that they did 

 just before that event. We have found, then, in our material no evi- 

 dence of a typical prophase leading up to the formation of the 

 spindle which is connected with the production of the second (the 

 nucleated) bud. 



During the period intervening between the formation of the first and 

 second buds the centrosomes sometimes present a condition that may 

 have a bearing on the interpretation of the process we are dealing with. 

 Either the distal or the proximal centrosome, or rarely both, becomes 

 elongated in a plane perpendicular to the axis of the spindle (Figures 

 10, 11), and in some instances a constriction divides it more or less 

 completely into two bodies. 



When the interzonal body has been detached, the spindle figure 

 again assumes the condition characteristic of a nucleus in the meta- 

 phase ; its cross section becomes greater, and the chromosomes, six- 

 teen in number, immediately undergo division. The small daughter 

 chromosomes, of the same size as each of the components of a dyad 

 previously described, migrate to the poles of the spindle, leaving 

 stretched between them interzonal filaments, which stain in iron 

 haematoxylin like the spindle fibres. Nearly up to the stage repre- 

 sented by Figure 12, nothing suggests an unequal division of the cell ; 

 but as soon as the chromosomes arrive at the poles of the spindle the 

 proximal end of the cell elongates and the chromosomes appear as a 

 deeply stained mass at the apex of a second finger-like process of 

 cytoplasm. The chromosomes at the opposite pole become surrounded 

 by a membrane, thus giving rise to a small typical nucleus. Between 

 these two nuclear bodies are seen the interzonal filaments together 

 with remnants of the more peripheral fibres already described in 

 connection with the account of the elimination of the interzonal body. 

 The finger-like process at the proximal end of the cell with the nuclear 

 mass at its tip continues to elongate (Figure 14), and eventually its 



