577 
member of the Palmellaceae. 
This investigation was carried out under the direction of Dr. G. S. West, 
to whom I wish to express my sincere thanks for his kindness in supplying 
me with material, and for many helpful suggestions in the course of the 
work. I also wish to thank Professor Hillhouse for his kindly advice and 
for revising the manuscript. 
DESCRIPTION OF PLATE XLIIX. 
Illustrating Miss Acton’s paper on Coccomyxa. 
Figs. 1-15 x 1000. p = pyrenoid. 
Fig. 1 . Isolated cells. The shaded portion represents the chloroplast. 
Fig. 2. Cells with mucous investment (indicated by dotted line) showing oblique fission. 
Fig. 3. Mother-cells containing four non-motile gonidia. 
Fig. 4. Subspherical aggregate of cells formed by development of non-motile gonidia in rapid 
succession ; ( a ) shows an early stage. 
Fig. 5. Formation of non-motile gonidia in a culture in 0*25 per cent. Knop’s solution. 
Fig. 6. Cells from a culture in 0.25 per cent. Knop’s solution, showing increase in size. 
Fig. 7. Cell from the same culture with two pyrenoids. 
Figs. 8-15. Material from a culture on damp sandstone. 
Fig. 8. a , Formation of four non-motile gonidia ; b , Three of these have formed zoogonidia. 
Fig. 9. a , b, and c show three stages in the formation of zoogonidia. 
Fig. 10. Cells containing four, eight, and sixteen zoogonidia respectively. 
Fig. 11. Fully formed zoogonidia on the point of escaping. 
Fig. 12. Zoogonidia. a , b , c , are macrozoogonidia ; d, e , microzoogonidia. 
Fig. 13. Generation of zoogonidia formed immediately from other zoogonidia without any 
period of rest. 
Fig. 14. (a) zoogonidium with cilia withdrawn ; ( b ) shows a later stage, the pyrenoid has 
increased in size and the cell has become more rounded ; in ( c ) the pyrenoid has divided. 
Fig. 1 5. Typical vegetative cell which appeared in the culture after a period of two months. 
