Flagellata and Primitive Algce, 113 
it becomes deeply bilobed and even divided into two (Fig.5, 1,2). 
In Chrysapsis, division often occurs within a gelatinous investment, 
while in Nannochrysis the formation of a palmella-stage is more 
pronounced and several divisions occur before the products of 
division become free by dissolution of the jelly. These simple forms 
show marked resemblance to some of the simpler Protomastigineae ; 
Chrysamceba is very similar to Mastigamceba and Oikomonas, apart 
from the absence of a chromatophore in the latter genera. 
The Chromulinaceae, forming the largest family of Chromuli- 
nales, include solitary and colonial forms, the former showing a 
elaboration of the protoplast as compared with the Chrysapsida- 
ceae ; there is usually a single basin-shaped chromatophore, but 
sometimes two or even more may be present. Among the solitary 
forms, Chrysococcus (Fig. 5, 15, 18) has a thick shell or perisarc 
closely investing the periplast, but with a small anterior opening 
for the flagellum, the periplast of some species is ornamented with 
wart-like out-growths, and there is either a basin-shaped chromato¬ 
phore or two lateral curved plate-like chromatophores, or several 
discoid chromatophores (Pascher, 99). A further elaboration is 
seen in the curious epiphytic genera Chrysopyxis and Stylococcus, in 
which the body is amoeboid and lies freely within a goblet-like shell 
or perisarc which projects freely beyond it, and is produced at the 
base into a hapteron; longitudinal division occurs within the shell, 
and one of the daughter cells escapes, produces a perisarc with an 
attaching process, and settles down ; the cell contains cellulose, 
and the “ flagellum ” is in reality a “ rhizopodium,” or branched 
filamentous pseudopodium, at any rate in Chryopyxis (Fig. 5, 26-30), 
which may be regarded as practically a Chrysamoeba that has 
become epiphytic and produced a shell; in Stylococcus (Fig. 5, 
23-25), the “ flagellum ” is unbranched, but differs from the normal 
type of flagellum in being motionless and is doubtless pseudopodial. 
The colonial genera of Chromulinaceae show an advance upon 
the Chrysapsidaceae, in that the palmella stage is more enduring, 
and in the genus Hydrums becomes dominant. In Chromulina 
Hokeana, division occurs in the motile state, and the products of 
two or three successive divisions remain coherent to form a four- or 
eight-celled motile colony, comparable with the ccenobia of Gottium 
and Pandorina, and thus representing the “Volvocine tendency” 
which has appeared independently in several distinct groups of 
Chrysomonads. In most species of Chromulina (Fig. 5, 9-14). 
however, division occurs in a resting palmella state (after the cells 
have lost their flagellum), giving rise to an indefinite mucilaginous 
mass ; the free flagellate cells are amoeboid and resemble Chrysa¬ 
mceba. A far more enduring and definite palmella state occurs in 
Hy drums (Fig. 5, 37-41)', the motile cells (“zoogonidia”) are of 
tetrahedral form, with the flagellum at the broader anterior end 
and on coming to rest lose the flagellum, become attached 
assume an ellipsoid form, secrete a mucilaginous stalk, and by 
repeated division give rise to an elaborately and regularly branched 
colony of considerable size. In this colony the cells are more 
crowded in the smaller branches than in the main axis and the 
larger branches ; the whole structure behaves like a multicellular 
plant, growth in length depends on single apical cells, and the zoo- 
gonidia are produced from the branches, two or four arising by 
division of a parent-cell. 
