Smith—Monograph of Scenedesmus. 
457 
The length of cells that I have isolated agrees well with 
the dimensions given by Schroder (length 20 p, width 15 p), 
but they are much narrower, the widest cells being 8 p. By 
comparing the length with the width in the figure given by 
Schroder, we find that the cells are about a third as wide as 
they are long, therefore being more nearly 6-8 p than 15 p 
wide. Under these conditions the form that I have isolated 
agrees perfectly with the S. acutiformis of Schroder. 
The number of cells in the colonies of my cultures varies 
from two (Fig. 89) to eight (Fig. 84) with four the predomi¬ 
nant number (Figs. 85-88). The ridges are quite prominent 
even from a side view and extend from one end of the cell to 
the other. They vary from one-half to one micron in width, 
and should be represented by two lines (Figs. 85-88) instead 
of by a single line as done by Schroder. Schroder has al¬ 
ready pointed out that the number of ridges on the cell can 
best be determined from an end view which shows that the 
terminal cells of the colony have four ridges. This, however, 
is not universal since instances were found where the ter¬ 
minal cells had but three ridges (Fig. 88). The median cells 
always have a single ridge on each side. 
GEOGRAPHICAL DISTRIBUTION 
EUROPE. England (G. S. West, 1899, 1904B; West and West, 
1901B). Germany (Fleering und Homfeld, 1904; Lemmermann, 
1908E; Schroder, 1897C; Selk, 1907; Volk, 1905). Ireland (Adams, 
1908; West and West, 1902B). Italy (Gugliemetti, 1910). Russia 
(Levander, 1899). Scotland (West and West, 1905). Sicily 
(Lemmermann, 1908A). Sweden (Borge, 1907A; Lemmermann, 
1904A). Switzerland (Chodat, 1902). 
AFRICA. Lake Nyassa (G. S. West, 1907). 
ASIA AND OCEANIA. Australia (Hardy, 1906; G. S. West, 
1909A). Java (Bernard, 1908). Johore (Bernard, 1909). Siam 
(West and West, 1902). Singapore (Bernard, 1909). 
AMERICAS. Pategonia (Borge, 1901B). United States (Borge, 
1909; Snow, 1903). 
15. S. costatus Schmidle. (PI. XXVI: Figs. 26-27.) 
Schmidle, 1895, p. 305; PI. XIV, Figs. 5-6. Schmidle, 1900A, p. 
(111). Dalla Torre und von Sarnthein, 1901, p. 35. Simmer, 
1901, p. 83. West and West, 1901B, p. 121. Bohlin, 1902, p. 44. 
Chodat, 1902, p. 216; Figs. 141A-141H. Lemmermann, 1902, p. 
(251). G. S. West, 1904B, p. 221. Borge, 1907A, p. 58. Migula, 
