1899] BRIEFER ARTICLES 311 
cell, being then cut off by transverse walls. The long gelatinous hairs 
observed in the material from the aquarium disappeared in smaller 
cultures. 
The chromatophores, of which there are many in each cell, are 
~ small oval bodies closely crowded near the membrane and imbedded 
ina highly refractive, almost gelatinous looking, liquid. Whether this 
s simply the protoplasm which surrounds all chromatophores, or 
vhether it is of some special composition was not determined. ok 
‘ingle pyrenoid is present near the middle of each cell, and this is 
surrounded by a starch envelope, somewhat irregular on the surface. 
The nucleus lies near the pyrenoid, and assumes more or less the 
shape of the cells in which it exists; that is, in the peripheral cells it 
nearly spherical, while in the central cells it is elongated. 
Though a disk shape is characteristic of the species when attached 
some solid substratum, it is by no means necessary to the plant, and 
“ens to be assumed only when the plant is attached. If it become 
tached (and it seems to be capable of living indefinitely in this con- 
ite the whole thallus loses all symmetry of structure, and forms 
“mply an irregular mass of cells the same as is noticed when the cen- 
yi becomes loosened from the substratum. If a plant be 
a. from the surface of the glass and put into a hanging drop 
diate ee In water or in Knop’s solution, there occurs an imme: 
and " ongation of the cells perpendicular to the plane of the disk, 
edge “¢ stand up, papilla-like, over the whole surface, even at the 
iin i. the cells had been most flattened. In one instance, 
in th our days, division parallel to the plane of the disk had occurred 
*€ cells, and these again divided in all directions, so that the sur- 
the oo eg _ as then covered with little clusters of cells without 
ent Ct eamealagf of arrangement, each cluster leading an independ- 
nee (fig. 6). 
had holds true if the development be watched from 
istic disk-for these become attached on coming to rest the mare 
Of the Satie. is produced (figs. 7, 8), but if they rest on the gic 
% agar, then x if they rest on a substratum less solid than ies 
thallus ig deta . development is identical with that when rf kale 
Somewhat cs @ fom a anid substratum, except that the cells ae 
ivision oa Tanging in diameter from 13 to 23 ae 7 
4 cel] into e 8 In these cells rather irregularly. A wall may so 
qual or unequal parts, while in other cases one OF 
