PLANKTON ALQ2E OF LAKE ERIE. 
385 
is of short duration, and immediately upon coining to rest they become spherical in shape, hut often 
retain the flagellum and the pigment spot after the spherical form is assumed. The germination 
takes place immediately (fig. xn, 6) , the cells increasing in size, and the two chloroplasts becom- 
ing divided into 4,8, and more as the size increases. Very often in old cultures and in vigorous 
cultures along the sides of the culture glass at the surface of the liquid the zoospores, instead of 
being liberated, germinate within the mother membrane and remain united in a mass long after 
the surrounding membrane disappears (fig. xn, 4). Before they are mature, however, they sepa- 
rate and have the same appearance as cells which come from the motile spores. 
Botrydiopsis oleacea Snow, new species. 
This species was first found in a culture from plankton material, but many cells taken to be 
the same were also found in fresh collections, the distinguishing characteristic being a large 
brownish-red globule near the center of each cell, which as yet has not been found in other 
plankton algae. The cells in the mature stage are either spherical, ovoid, or lemon-shaped, but usu- 
ally become more rounded in later stages of existence (fig. xm, 1,2). The ovoid or lemon-shaped 
cells were most often noted when the cells had attained about two-thirds their natural size, the 
latter shape being conspicuous on account of the wart-like projection on one or both ends of the 
cell (fig. xm, 3, 4). The cause of these excrescences was not determined. They occurred on some 
but not on all cells of the same culture. The largest cells were broadly ellipsoidal, or almost 
spherical, and 13.5 M in diameter. 
For some months after this form was placed in culture it was regarded as a Chlorococcuin , so 
nearly did the general appearance agree with the characteristics of that genus, the only striking 
differences being the shape, the absence of the pyrenoid, and the presence of the large red globule 
near the center. On account of the very granular appearance of the cell, due to small globules of 
oil, the chlorophyll was thought to be in a single chloroplast, as in Chlorococcum, and the presence 
of numerous small chloroplasts characteristic for Botrydiopsis was not suspected until the entire- 
development was traced. Different phases of reproduction, however, showed such a resemblance 
to Botrydiopsis that the chloroplasts were again examined. In some young cells it was evident 
that there were several instead of one in each, though these were not distinguishable in mature 
cells further than that certain areas seemed slightly darker than others. Many mature cells 
appeared almost black, so filled were they with the minute globules of oil. This oil became dis- 
solved in absolute alcohol. Iodine with sulphuric acid showed the membrane to be of cellulose, 
and hsematoxylin brought to view the single small nucleus a little to one side of the center. 
The red globule which was always present was at first taken to be a particle of red-colored 
oil, but, on account of the color, the ordinary tests could not be used satisfactorily. When 
absolute alcohol was added the globule disappeared. Its position is apparently underneath the 
layer of chloroplasts. It was noticed that in the formation of the zoospores the globule did not 
become divided, but remained in the center throughout the whole process, though it apparently 
grew somewhat smaller as the process continued. When the zoospores were liberated it was cast 
out with them and had no further connection with the organism. This suggested the appearance 
described by Klebs (’96), in his work on Protosiphon and Hydrodictyon, where the cell sap did 
not enter into the process of zoospore formation and was cast out in the same way when these 
were liberated. The same phenomenon has also been noted by the author in an undescribed 
species of Botrydiopsis. 
The zoospores, of which 2, 4, 8, 16, or more are formed in a cell, arise through the repeated divi- 
sion of the entire cell contents, except the red globule, until the final number of zoospores is reached 
(fig. xiii, 5, 6, 7). The zoospores are characteristic for Botrydiopsis, having but a single ciliuin 
and being very amoeboid in their motion (fig. xiii. 8) . Though their shape is constantly changing, 
the general form is pear-shaped, broadly rounded at their posterior end, and tapering toward the 
cilium. In length they vary from 5 to 7.8 /< and in breadth from 3 to 5 p at their broadest extrem- 
ity. As in the mature cells so in the zoospores the chloroplasts are obscured by oil. In the anterior 
end, just at the base of the flagellum, is a very refractive dull red spot, but it could not be deter- 
mined whether this was the ordinary pigment spot of the zoospore or the beginning of the red 
globule found in the older cells. The zoospores are active and seek the light. On coming to rest 
they become rounded and the chloroplasts become more distinct than at any other stage of their 
F. C. B. 1902-25 
