Hazen: Lire History oF SPHAERELLA LACUSTRIS 241 
but more stable; its value probably lies in this stability and per- 
haps also in its protective and heat-producing power. 
= IO. The zooids are generally strongly attracted toward the light. 
II. Some interruption of development such as desiccation or 
freezing is necessary for preservation of vitality. 
12. Sphaerella lacustris is to be regarded as a plant because 
of the possession of a cellulose cell-wall and chlorophyl and the 
holophytic mode of nutrition. 
I3. The“ red snow " 
distinct from S, /acustris on the grounds of morphological and 
species Sphaerella nivalis is regarded as 
physiological differences. 
LITERATURE 
. In the following list the important papers relating to the life 
history and nomenclature of Sphaerella lacustris are collected. It 
has been intended also to note all original illustrations. 
e memoir of Braun ('51) gives by far the clearest and most 
accurate account of the life history, but it has been little used by 
later writers. The work of Cohn (50) which has been chiefly 
drawn upon for brief accounts, though of great value, is neverthe- 
less not so clear, and has been misrepresented in translations and 
abstracts. There are several minor accounts in text-books, which, 
possessing no merit of originality and in some cases the positive 
demerit of inaccuracy, have not been included in this list. 
BENNETT, A. W. & Murray, G. Handbook of Cryptogamic Botany, 
415, 416. London, 1889. 
BERLESE, A. N. & De Towr, G. B. Intorno al genere Sphaerella di 
Cesati e De Notaris ed al Omonimo di Sommerfelt. Atti Reale 
Ist. Ven. d. Sci. VI. 5!: 221-228. 1887 
Braun, Ar. Betractungen über die Ersheinung der Verjüngung in 
der Natur. Leipzig, 1851. (Translation by A. Henfrey, Bot. and 
Phys. Mem. Ray Soc. 1853.) (Abstract in Cooke, M. C. Brit. 
Fresh-Water Algae 51—54. 1882 
BRAUN, AL. Chlamydococcus pluvialis bei Berlin. Bot. Zeit. 10: 
245-247. 1852. 
BUürscHLi, O. Protozoa, 2: 836. Leipzig, 1884. 
Busk, G. Abstract of Cohn’s Natural History of Protococcus pluvialts. 
Bot. and Phys. Mem. Ray Soc. 1853. 
CHopaT, R. Sur la flore des neiges du Col des Écandies.' Bull. Herb. 
Boiss. 4: 880-889. 1896. 
