DIVISION OF COLLAE-CELLS OF CLATHRINA CORIACEA. 629 



come to lie at the extreme surface of the cell. The spindle 

 is lodged in that portion of the cell which we have termed 

 the neck in a previous section, and the centrosoraes ai-e 

 situated about midway between the origin of the still per- 

 sistent collar and the flange. The chromosomes appear 

 massed together, and are difficult to distinguish individu- 

 ally when the equatorial plate is seen in side view (figs. 17, 

 18), but can be seen better in cells cut parallel to the plane 

 of the equatorial plate (fig. 22). The number of chromosomes 

 appears to be about sixteen. 



At this period, while the equatorial plate is still simple and 

 undivided, an important event takes place. From the cen- 

 trosomes at the two poles of the spindle the two daughter- 

 flagella grow out, appearing as two minute hair-like pT'OJec- 

 tions from the surface of the cell (figs. 18-21). This stage 

 is a very common one, and it is, in fact, rare to find a collar- 

 cell with a mitotic spindle without the two daughter-flagella 

 projecting from the two centrosomes; this indicates that the 

 first formation of the flagella must be an extremely rapid one. 

 Sometimes only one daughter-flagellum is to be seen, but in 

 such cases the cell is usually slightly oblique, and the missing 

 flagellum has probably been cut off by the knife in cutting 

 the section. The two new flagella are formed entirely outside 

 the original collar, which is still persistent. The condition of 

 the collar is best studied in osmic-picrocarmine preparations 

 (figs. 42-45), in which it is seen that the formation of the nuclear 

 spindle causes the cell to become much broader, with the 

 result that the base of the collar is greatly stretched. The 

 thicker portion of the collar, below the hoop, retains its form 

 more or less, but the portion above the hoop tends to collapse 

 and fall together. 



From the stage with the single equatorial plate the diastei"- 

 stage arises in the usual way (figs. 23, 24). It is remarkable 

 that we have succeeded in finding but fcAv specimens of the 

 diaster-stage, and, unfortunately, most of those have been cut 

 obliquely or horizontally, and hence do not show well the 

 relation of this stage to the cell as a whole. Fig^s. 23 and 24 



