378 
BULLET!^ OF THE UNITED STATES FISH COMMISSION. 
toward the opposite end of the daughter cell (fig. v. 4). The nuclei retain this position in the cell 
for some time after the cells are liberated (fig. v, 6). Before liberation each cell becomes invested 
with a membrane. 
The daughter ccenobium is set free by the membrane of the mother cell becoming ruptured 
from the middle of the base to the apex, so that one longitudinal half is loosened and thrown 
back like a lid, thus setting free the daughter individuals (fig. v, 7). Under conditions where but 
little gelatinous substance is present and only single coenobia are produced, many such empty 
membranes are found in the surrounding medium. Where the gelatinous substance is in great 
abundance, and large plates of cells are formed, these remnants of membranes for two or more 
generations may be found clinging to the sides of the cells. 
Physiology . — This species of Staurogenia is greatly affected by the kind of substances available 
for nutrition. Cultures were made in a large number of different solutions — Knop's solution, sugar 
solution, decoctions of mixed vegetable and animal matter found in the plankton, decoctions of 
pure vegetable matter, and decoctions of earth. Other solutions were also used which will be 
referred to later. In most cases cultures were made in a number of different concentrations of the 
same solution, so that amount of substance, as well as kind, was taken into consideration. For 
rapidity of increase the organic solutions seemed to be of far more importance to the species than 
the inorganic, and the solutions found most favorable to this were the decoctions of organic matter 
from the plankton, though a solution from decaying peas was also favorable. In fresh cultures in 
these solutions the plates usually consisted of sixty-four cells (fig. v, 1), one-lialf usually being 
folded back upon the other, but in the older cultures, where the material had increased greatly, 
the plates were small, consisting in a large number of cases of sixteen cells (fig. v, 2). 
Knop's solution, which is a favorable medium for a large number of algse, did not prove 
favorable to either reproduction or development in this species. In cultures of 0.4 per cent, 0.1 
per cent, and 0.05 per cent of this solution, very little increase took place, the color was pale and the 
regularity of the coenobia was lost, while, owing to the absence of gelatinous substance, the large 
masses were never formed. In 0.1 per cent and 0.05 per cent growth was more abundant than in 
the 0.4 per cent. The cells showed no regularity of arrangement, however, and no trace of 
gelatinous substance could be detected even when treated with tannate vesuvine (fig. v, 3). In 
the decoctions of earth development was normal, increase was rapid, and the general condition was 
vigorous. In a 2 per cent sugar solution the species lived but a short time. In cultures where 
nutrition had become exhausted the cells assumed a dull rust color, due to the presence of oil. 
This probably was a resting stage, though all attempts to resuscitate it after it had been dried in 
this condition failed; when not dry, however, the green color soon returned if fresh nutrient 
solution was added. 
As this species did not flourish in Knop's solution the question arose as to what element in the 
compound was detrimental to the alga and prevented development. It was thought that it might 
be the large amount of calcium in Knop’s solution which produced this effect, and to determine 
this point Knop’s solution was then made without calcium, and a solution without calcium used 
by Oelmann in the cultivation of sphagnum was tried. Cultures were made in various concen- 
trations of both these solutions with the following results: In a 0.4 per cent Oelmann's solution 
development was far more natural than under any other artifical conditions, the group of cells 
being much larger than in other cultures. The same appearance, though to a less extent, was 
found in other concentrations — 0.1 per cent and 0.05 per cent of the same solution and also in 0.5 
per cent and 0.25 per cent of Knop's solution without calcium. Apparently, then, calcium inter- 
feres with development, and in nature the organism probably would not find a habitat in water 
containing much of this element, but would seek a soft water rather than a hard. The number of 
clusters which were formed in these cultures without calcium was few in comparison to the 
number in organic solutions and the cells were a trifle smaller. The direct cause of the develop- 
ment being higher where the individuals are fewest was not determined in this case, but it seems 
to be true of the other algse as well as of this. 
Fusola viridis Snow, new genus and new species. 
In the natural condition, as found in a stagnant pond in Middle Bass Island, in Lake Erie, the 
cells of this species were single, fusiform in shape, and sometimes slightly sigmoid (fig. vi, 3) . They 
vary from 27 to 39 // in length and 8.5 to 21 y in width. A medium size is 28.5 y long and 8 y broad. 
