I 12 
F. Cavers. 
The Chrysomonads are characterised by a peculiar endogenous 
method of cyst formation. Before a definite cyst appears, there is 
visible within the protoplast a membrane covered by an amoeboid 
protoplasmic layer (Fig. 5, 11-14), which produces sculpturing on the 
outer surface of the cyst membrane, but later this protoplasm 
retreats within the membrane through a pore which has been left, 
this pore being afterwards closed by a plug which in some cases 
consists of cellulose; the membrane usually contains silica. A 
similar method of cyst formation occurs in certain colourless 
heterotrophic genera which have hitherto been placed in the 
Protomastigineae, and on this ground, as well as on account of 
other cytological resemblances, it is suggested that these forms 
should be transferred to the Chrysomonads. These forms, which 
may be regarded as colourless derivatives from normal autotrophic 
Chrysomonads—corresponding with the colourless forms ( Polytoma, 
etc.) included in the Volvocales—belong to the genera Monas, 
Oi/conionas, Dendromonas, Antopliysa, Cephalothamnion, etc. It 
would appear that further investigations will lead to a consider¬ 
able number of genera being transferred from the Protomastigineae 
to the Chrysomonads, and doubtless to other groups of pigmented 
Flagellata, if we accept the view that where colourless and 
coloured Flagellates show close agreement in every character 
save the presence or absence of assimilatory pigments, the 
colourless forms are to be regarded as having arisen from the 
coloured as an adaptation to a heterotrophic mode of nutrition. 
The recent work of Pascher, Scherffel, Senn, and others has 
shown that the Chrysomonadineae (in the wider sense, as defined 
by Pascher) form a remarkably diversified group, in each order of 
which various parallel developments may be traced, starting from 
relatively simple free-living and usually small forms. The chief of 
these parallel developments are the formation of motile colonies 
analogous with those of the higher Volvocales, and of variously con¬ 
structed non-motile colonies corresponding with those of the 
Tetrasporaceae and other families of Protococcales characterised 
by aggregation of the cells into mucilaginous masses; the occurrence 
of amoeboid forms and of amoeboid phases, the latter perhaps to he 
regarded as reversions to an ancestral condition ; the lobing, division 
and further elaboration of the primitively indefinite and reticulate 
or basin-shaped chromatophore ; the coordination of the contractile 
vacuoles to form a pulsating vacuole system similar to that seen in 
the Chloromonadineas and Euglenineae ; the substitution of solid 
carbohydrate assimilates (paramylum and starch) for oil and 
leucosin; the elaboration of the outer protoplasmic layer into a firm 
periplast and finally into a definite membrane (in some cases con¬ 
sisting of cellulose) which may form either a close-fitting or an 
outstanding and cup-like perisarc ; the outgrowth of tentacles from 
the periplast; and the development of sculpturings and of various 
excrescences (ridges, spines, etc.) on the cell-wall. 
The Chromulinales include the simplest forms of the Chryso- 
monadineae. In the lowest family, Chrysapsidaceae, the cells are 
free-living and are amoeboid ; in Chrysapsis the chromatophore is an 
indefinite reticulate peripheral sheet, while in Chrysamctba and 
Nannoclnysis it is basin-shaped, though in some species of Chrys- 
