1186 Wisconsin Academy of Sciences, Arts and Letters. 
tions of different concentration had no effect on the form of 
the colony, but they did affect the individual cell, since Senn 
found the stronger the solution the more nearly spherical were 
the cells. Artari (4) studied Dactylococcus infusionum ISTaeg., 
as a separate form and did not obtain Secenedesjnus-like colon¬ 
ies, although he grew the alga under various conditions. 
One of the forms Beverinck worked with in his first pure cul¬ 
tures (5) was Scenedesmus acutus. Beverinck found that an 
abundance of organic food material cause the cells of S. acutus 
to lose their acicular shape and become more nearly spherical. 
He makes no mention of the formation of chain-like colonies. 
The cellular arrangement of Scenedesmus acutus underwent 
considerable modification in Grintzesoo’s pure cultures. He 
describes three different development phases. There may be 
the ordinary Scenedesmus coenobe of 2, 4, or 8 cells, all arranged 
in a single plane. At other times the cells exist singly, the indi¬ 
vidual cells resembling Ankistrodesmus (Baphidium). Again 
the cells are arranged end to end in the form of small branching 
chains of cells. An alga with acicular cells arranged end to 
end in a branching flament has been given the name of Dactylo¬ 
coccus infusionum by Haegeli (32). Grintzesco believes that 
the branching colonies he obtained in his cultures are wholly 
identical with the Dactylococcus infusionum of Haegeli. He 
therefore concludes that Dactylococcus infusionum is not a spe¬ 
cific form but merely a 1 growth condition of 8 . acutus. He 
finds that solid media, as agar or gelatin combined with a nutri¬ 
ent mineral solution, hinders the formation of the plate-like 
eoenobes of Scenedesmus but favors the formation of the Dacty¬ 
lococcus condition instead. When the alga is grown in a li¬ 
quid medium the ordinary eoenobes are formed in the first few 
days, but when the cultures are some weeks old they begin to 
have the cells arranged end to end in branching chains. If 
material forming chains of cells in an old liquid culture be put 
in a fresh liquid medium there is a return to the formation of 
the plate-like colonies for a while. He considers the Dactylo¬ 
coccus condition an adaptation for increasing the surface for res¬ 
piration when the medium is poor in oxygen, or rich in mineral 
matter. 
