1166 Proceedings of Royal Society of Edinburgh. [sess. 
1900. Zschokke (F.), “Die Tierwelt der Hochgebirgseen,” 
Denkschr. d. Schweiz, naturf. Ges. Zurich , xxxvii. p. 1. 
1904. Zykoff (W.), “ Zur Crustaceen fauna der Insel Kolgujev,” 
Zoolog. Anzeiger, xxviii. p. 337. 
Explanation of Plate I. 
Figs. 1-7. Melosira islandica, O. Muller, n. sp. : — 
1-5. Chains showing the successive stages of the auxospore 
formation. 
6. Two-celled auxospore chain. 
7. Eight-celled auxospore chain. 
Fig. 8. Oocystis crassa, Wittr., forma. 
Figs. 9-10. Cyclotella comta, Kiitz. ; a small and a large cell, valvar 
view. 
Figs. 11-20. Peridinium aciculif erum, Lemmerm. : — 
11. A cell in Gymnodinium stage with mucilaginous en- 
velope. 
12. Another Gymnodinium cell with large oil drops. 
13. The formation of two daughter cells. Here and in 
fig. 12 the envelope has been omitted. 
14-15. A specimen in two views. 
16. Another specimen in dorsal view. 
17. Side view. 
18. Ventral view. 
19. A specimen of which the contents are bursting. 
20. Resting cyst. 
The microscope used is Zeiss’s large microscope (Stand la), with 
compensating eye-pieces and apochromatic objectives. The figures 
are drawn with Abbe’s camera (No. 44a). The magnifications are 
as follows 
Figs. 1-7, 11-20, objective 1*25 x 2*5 mm. Comp, ocular, 8 
(Water immersion.) 
Fig. 8, objective 0‘95 x 4-0 mm. Comp, ocular, . . 8 
Figs. 9-10, objective P40x2‘0 mm. Comp, ocular, . 8 
(Oil immersion.) 
