388 BULLETIN OF THE UNITED STATES FISH COMMISSION. 
forms were found with conical or oval cells, which undoubtedly were the Gomphospheeria lacustris 
of Chodat, °98, and possibly the Cwlospherium naegelianum as figured by Borge, 00. 
The resemblance of the form described, as well as of these other forms, to certain species of 
Gomphospheria, such as Gomphospheria lacustris Chodat, is fully recognized by the author, but 
a study of the well-known Gomphospheria aponina Kitz, and of the well-recognized species of 
Celospherium has caused the writer to place it under the genus Coelospherium rather than Gom- 
phospheria. From a study of the true Gomphospheria each cell, instead of simply resting at the 
extremity of the stalk, seems to lie in a capsule of the same substance as the stalk and continuous 
with it, as has been figured by Schmidle (01). The outer boundary of this capsule is sharply out- 
lined about each individual cell, an appearance which has not been noted in any of these other forms. 
Further, it would seem that all Cewlospherium species, although the central gelatinous sphere 
appears homogeneous, really have at the center the dichotomously branched framework of denser 
gelatinous material. If a colony of Celospherium kutzingianum Naeg. be crushed under a cover 
glass, it will first divide into two, then into four, and then into eight equal parts, each becoming 
spherical immediately, just as would occur if left to take its normal course, whereas if it were 
perfectly homogeneous the mass would crush without any system. In all cases of multiplication 
where the colony becomes divided into two, evidently the two branches of the first dichotomous 
division at the center become detached from each other, and the two halves, unable to hold together 
by the less dense gelatinous substance, are set free. 
Chroococcus purpureus Snow, new species. 
The cells are spherical, or, just before division, somewhat elongated, usually arranged two by 
two in colonies of four or eight, all cells of which are more or less separated from each other 
according to age, and held in place by an enveloping gelatinous substance. The diameter of the 
cells is 13 4; the membrane is thin. The color in the natural condition is grayish purple (fig. Xv). 
This species is distinguished from the Chroococcus multicoloratus Wood in being larger, the 
cells more loosely associated into colonies, and in possessing a more decided purple color. When 
it was first noted in the plankton it was thought it might be a Chroococecus limneticus Lemm.. 
which is so abundant in the plankton and which differs from it only in color, that being a blue- 
green, while this is a purple. Though the two species could not be maintained in artificial culture 
for observation during any extended period of time, still, in an organic solution C. purpureius was 
kept in a healthy condition for a number of weeks, during which another culture of Chroococcus 
limneticus, under identical conditions, was kept for comparison. This was long enough to convince 
one that the two forms were not the same and that the purple did not change into the blue-green. 
Both this and Chroococcus limneticus, however, did vary their hue somewhat, according to condi- 
tions, both taking on a much darker shade of their respective colors as the concentration of the 
organic substances in the culture medium was increased. In old solutions both became paler, the 
purple form assuming something of a brown tinge and the blue-green a yellowish gray. Under no 
conditions, while in a healthy state, did the two alge assume the same appearance. In both species, 
however, when cells lost their vitality, the contents contracted, the outline of the enveloping gelat- 
inous substance became sharply outlined, and the color became a deep blue-green (fig. XVIII, «). 
In this condition they could not perhaps be distinguished. Whole clusters of them were found in 
the plankton, and until this phase of these two forms was noted they were supposed to be a species 
of Gleocapsa, but were probably only pathological stages of one of these species. 
DESCRIPTIONS OF NEW SPECIES. 
Chlamydomonas gracilis Snow, new species (fig. 1). 
Cells cylindrical, rarely oval or spherical, 10.5 to 13 4 long, 5 to 6.5 2 broad, color a dull bluish 
green; cilia 2, about 14 times as long as the cell: pigment spot a dull red disk, often equally distant 
from the two ends; pyrenoid at the extreme posterior end. (Gametes (?) oval in shape and some- 
what smaller than the vegetative individual. Locality. plankton of Lake Erie. 
Chlamydomonas communis Snow, new species (fig. I1). 
Shape, ovoid, cylindrical or ellipsoidal, 10.5 to 13 4 long, 6.5 to 8 sc broad; color a light yellowish 
green, the pyrenoid near the center; pigment spot an inconspicuous red rod: cilia 2, slightly longer 
than the cell; division longitudinal. Locality, plankton of Lake Erie. 
a 
