384 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
If the material be cultivated in a 2 per cent Knop’s solution, almost all individuals produce 
gonidia; that is, the contents become divided into two, four, or eight portions, as if to produce 
zoospores, and these divisions, instead of becoming liberated as zoospores, become invested with a 
membrane and germinate while still within the mother membrane. These in turn may produce 
gonidia before they become liberated, so that two, and possibly three, generations may be included 
within a single cell wall (fig. xi, 2). When cultivated in organic solutions and in 0.4 per cent 
Knop’s solution, oblong gonidia are formed, but the enveloping membrane becomes gelatinous, and 
the alga passes into a palmella condition (fig. xi, 3). 
If the material be transferred from a nutritive solution to water, zoospores are formed. If 
transferred from 0.2 per cent or 0.4 per cent Knop's solution, the shape of the zoospores is cylin- 
drical (fig. xi, 4). They measure 0.5 to 8 y long and 2.5 to 3.25 y broad and they move with a rapid 
motion. If the same material be transferred from 0.4 per cent Knop's solution to organic solution, 
the zoospores are oval (fig. xi, 5), 7.8 to 10 y long and 5.2 to 6.5 y broad, somewhat amoeboid 
in nature, and they move with a slow, lethargic motion. Apparently they are the cells which, if 
they had not been transferred, would have produced gonidia. The structure in both cases is the 
same, there being a concave chloroplast in which is embedded a pyrenoid about equally distant 
between the two ends. At the anterior margin of the chloroplast is a red pigment spot. There 
are two cilia slightly longer than the cell, and at the base of these, two pulsating vacuoles. The 
zoospores become liberated by the mother membrane becoming gelatinous. In the case of the 
smaller cylindrical ones, as they expand, the enveloping membrane suddenly gives way at one 
point and the spores are liberated either in mass or singly. With the larger oval ones the process 
takes place more slowly. They arise by successive division of the contents of a cell (fig. xi, 7). 
Although there is a difference in the size of these two kinds of zoospores, there is no indication 
that these represented distinct macrozoospores and microzoospores. Apparently the larger size is 
more of an abnormal condition of the zoospores, as in all respects the cylindrical form seemed the 
more natural. 
The cells in the palmella condition and also the large zoospores resemble greatly Chlamydo- 
moncts , but the absence of a membrane in the motile form, the short period of motion, and the 
mode of growth of the alga in the inorganic solutions all showed a resemblance to Chlorococcum. 
Botrydiopsis eriensis Snow, new species. 
The younger stages of this species resemble that of Botrydiopsis arhiza, described by Borzi 
’95, but the later stages differ from that species. The cells are spherical, and when mature have a 
diameter of 18 to 21 y. In the younger stages the chromatopliores are more or less hexagonal 
disks, and are closely applied to the membrane, with spaces between them (fig. xii, 2, 3). In the . 
older stages the chloroplasts are relatively smaller, more elongated, and more crowded (fig. xii, 1). 
The membrane, which is thin, gives the characteristic reaction for cellulose with iodine and 
sulphuric acid. Within the cell no starch, pyrenoid, or oil is present, and the single small nucleus 
lies near the center. 
The reproduction coincides in the main with that of Botrydiopsis arliiza Borzi, usually 16 or 32 
zoospores being formed within a cell (fig. xii, 7). The successive stages of their formation were 
not observed, but it is probable that they arise from the repeated bipartition of the contents of the 
cell, as in other species of Botrydiopsis. In the mode of liberation of the zoospores this species 
deviates from Botrydiopsis arhiza and from other known forms of Botrydiopsis, where the zoo- 
spore mass, together with the inner layer of the enveloping membrane, escapes gradually through 
a small opening in the outer layer of the membrane. In this species the whole mass remains within 
the outer layer until both layers become gelatinous, and after a short period of motion within the 
membrane the zoospores one by one break through the membrane and escape. 
The zoospores (fig. xii, 5) are 5.2 y long, 2.5 to 3.25 y broad, and they possess all of the char- 
acteristics of Botrydiopsis zoospores. They are very amoeboid, changing their shape constantly 
as they move. Two elongated chromatophores are present, lying on opposite sides of the cells. 
One projects farther toward the anterior end than the other, and at the anterior extremity of this 
lies the pigment spot. A single flagellum is present. During the amoeboid movements, when the 
protoplasm happens to project at the anterior end beyond the chloroplast, two contractile vacuoles 
may be seen, but they are discernible only under these conditions. The motion of the zoospores 
