328 EXPLANATION OF THE PLATES. 



the interior, the nature of which is doubtful; between 

 the two, and more to the side, exists a lighter space 

 (frequently observable). 



Fig. 9. A similar cell, in which the dark-green portion 

 of the contents forms a pretty sharply circumscribed 

 mass with a constriction in the middle. 



Fig. 10. The same cell turned one quarter round, the 

 green mass appearing narrower and with a bright spot 

 beside it. 



Fig. 11. Another cell in the same position, with a still 

 more compressed green body in the interior, reminding 

 us of the genus Mesotanium, Nag. ('Einz. Algen.,' 

 t. iv, B.) 



Fig. 12. The same cell seen from above. 



Fig. 13. A similar cell, in which the plate-like green 

 mass is interrupted in the middle. 



Fig. 14. Two very short cells, shortly after their pro- 

 duction by division, with plate-like compressed green 

 masses placed obliquely in the interior. 



Figs. 15 — 16. Rows of cells in contact, without dis- 

 tinguishable enveloping membranes, such as are some- 

 times produced by rapidly succeeding divisions in very 

 active vegetation. The arrangement of the cells in this 

 case shows that the division constantly occurs only in 

 one direction. 



Figs. 17 — 20. Cells treated with tincture of iodine, 

 whereby the green masses in the interior are coloured 

 brownish, and a dark brown nucleus becomes visible, 

 which, however, does not appear sharply defined, and 

 certainly contains no starch. 



Fig. 21. A cell preparing for conjugation, furnished 

 with a lateral wart-shaped projection. 



Fig. 22. Two similar cells in contact by their wart- 

 shaped projections. 



Figs. 23 — 27. Cells conjugated by union and anas- 

 tomosis of the lateral processes, with the connecting 

 piece of variable length. 



Fig. 28. The same, but one cell crossing the other. 



