DIVISION OF COLLAR-CELLS OF CLATHKINA CORIACEA. 637 



EXPLANATION OF PLATES 25 and 26. 



Illustratino^ Miss Muriel Robertson and Mr. E. A. Minchin's 

 paper on ''The Division of the Collar-cells of Clathrina 

 coriacea (Montagu) : A Contribution to the Theory 

 of the Centrosome and Blepharoplast." 



[All the fignves ai-e drawn from sections of material fixed with 

 Hermann's fluid and stained by Heidenhain's iron-lisematoxylin method ; 

 t'le outlines were traced with the camera lucida at a magnification of 2000 

 linear, with the exception of figs. 36 and 37, which are magnified 3000 

 linear.] 



PLATE 25. 



Fig. 1. — Six collar-cells in their natural arrangement ; five of them 

 iire in the i-esting state ; the sixth (d) shows the nucleus in its migration 

 towards the blepharoplast, and has a very short flagellum. 



Fig. 2. — Early stage in the upward migration of the nucleus ; the 

 blepharoplast in the act of division, with shortened flagellum. 



Fig. 3. — Similar stage to the last, the blepharoplast distinctly divided, 

 the nucleus with two karyosomes. 



Figs. 4 and 5. — Stages showing the nucleiis in close proximity to the 

 Islepharoplast and distinctly flattened on the side nearest the blepharo- 

 plast, from which two streaks are seen to come down to the two ends of 

 the flattened border of the nucleus ; these two streaks appear to he 

 the optical section of a cone-shaped figui-e. In fig. 4 the flagellum is 

 seen to be still present, but shortened ; in fig. 5 no flagellum is seen and 

 the blepharoplast is divided. 



Fig. 6. — Stage showing the divided blepharoplasts connected by a 

 centrodesmose ; the flagellum is still present and of fair length. 



Figs. 7, 8, and 9. — Stages showing complete division of the Wepharo- 

 plast with persistent flagellum in each case ; the two daughter-blepharo- 

 plasts in each dividing cell have travelled inwards and placed them- 

 selves at opposite sides of the nucleus, drawing in with them the root of the 

 flagellum, and the free portion of the flagellum has its base surrounded 

 by an iipgrowth from the apex of the cell. In fig. 7 the adjacent rest- 

 ing cell is drawn for comparison ; in the dividing cell a centrodesmose 

 is seen between the two blepharoplasts. and there are also indications of 

 a streak running down from one of the l;>lepharoplasts to a granule in 

 the body of the cell, but this streak appears to be due merely to the 

 arrangement of vacuoles in the cytoplasm, and not of the nature of a 



