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. 1 1 . 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. 



