338 ETHEL NICHOLSON BROWNE 



In younger spennatocyte cells, as I have described, there is 

 besides the scattered mitochondria, a flat plate of mitochondrial 

 material lying just outside the nuclear membrane, and a mass 

 of 'mitochondria projecting from it into the cytoplasm. When 

 cells of this type are contrifuged, this plate and mass of mito- 

 chondria remain in position, the rest of the mitochondria are 

 driven to the distal pole (fig. 3). In these young cells, there is 

 an aggregation of oil drops at the extreme centripetal pole; these 

 can be distinguished only in the living material, probably being 

 dissolved in the process of fixing and staining. The nature of 

 these drops has been determined by means of Soudan III. The 

 oil drops are not present in the older spermatocyte cells, having 

 apparently been used up during the growth of the cells. 



In the dividing cells, the mitochondria are likewise thrown to 

 the distal pole by the centrifuge. The spindles and asters are, 

 in many cases at least, perfectly normal and are not interfered 

 with by the shifting of mitochondria, but lie in approximately 

 the normal position in the clear protoplasm. Since it has not 

 been determined how long one of these cells normally takes to 

 divide, it is not possible to say whether the chromosomes actu- 

 ally pass to the poles while the cells are in the centrifuge, but 

 various anaphase stages have been found in the centrifuged cells 

 showing that the chromosomes are undergoing normal division. 

 The spindle axis may lie in any direction with reference to the 

 mitochondrial mass. In figure 4, the spindle axis is approxi- 

 mately parallel to the mitochondrial mass; in figure 5, approxi- 

 mately perpendicular. Figure 6 shows a spindle in polar view 

 and its relation to the mass of mitochondria. In some cases, 

 a few of the mitochondria apparently get caught by the spindle 

 or asters and thus appear on the centripetal side of the division 

 figure (figs. 5 and 6). 



When the cells are centrifuged and then left in Ringer's solu- 

 tion for several hours or even overnight, the materials do not 

 become redistributed over the cell, but they remain in the posi- 

 tion induced by the centrifuge. 



It is of interest to compare the centrifuged spennatocyte cells 

 with centrifuged egg cells. In a number of marine eggs, it has 



