338 EDWIN G. CONKLIN 



of the yolk may have been driven to this pole and most of the 

 cytoplasm to the opposite pole (figs. 83 to 91). 



Similarly, resting nuclei and centrospheres do not move freely 

 through the cell under the influence of centrifugal force, but are 

 evidently limited in their movements by attachments similar to, 

 but less strong than, the astral radiations of the mitotic figure. 

 The centrosome is always closely attached to the chromosomes, 

 the centrosphere to the resting nucleus, and it is very difficult to 

 separate the two completely. Furthermore, both centrosome 

 and centrosphere are attached by astral radiations to a free sur- 

 face of the cell and in the telophase of the division this place of 

 attachment is carried as near as possible to the animal pole. 

 Consequently, throughout the resting period the centrospheres 

 are attached on one side to the nucleus and on the other to the 

 free border of the cell lying nearest the animal pole; these at- 

 tachments persist even in centrifuged eggs and although 

 nucleus and centrosphere may be forced away from the animal 

 pole side of the cell, these attachments are not destroyed, but are 

 merely stretched, as is shown by the lane of cytoplasm lead- 

 ing toward the animal pole, by the elongation of the centro- 

 sphere in this direction and by the return of centrosphere and 

 nucleus to their normal positions after centrifuging (figs. 87 to 

 90). In figures 84 and 85 the axis of centrifuging was parallel 

 with the first cleavage plane and nearly at right angles to the 

 egg axis; in figures 83, 86, 87, 89, 90, 92 the axis of centrifuging 

 was in the chief axis of the egg, the animal pole being centrifugal 

 and the vegetal pole centripetal; in figures 88, 91, 96 the axis of 

 centrifuging was at right angles to the first cleavage plane and 

 to the egg axis; in figures 95, 97, 98 it was at right angles to the 

 second cleavage plane and to the egg axis. These axes of cen- 

 trifuging are all the principal axes of the egg in which an abnor- 

 mal distribution of cell substances can be brought about, and 

 yet in every case the centrospheres lie between the nucleus and 

 the animal pole and in some instances the strands connecting 

 these can be clearly seen (figs. 87 to 90, 95 to 98). Figure 86 

 is especially interesting because the mid-body (MB) and spindle 

 remnants are present as well as the nuclei and centrospheres. 



