Flagellata and Primitive Algce. 187 
show a tendency to the formation of flinty skeletons (e.g.,Mallomonas, 
Chrysosphcerella). The Coccosphagrales (Coccolithophorid^e, 83, 86, 
87) are perhaps derived from simple Chromulinales; in general 
morphology they resemble forms like Cluysococcus, but with a 
peculiar armour consisting of calcareous plates instead of a 
homogeneous perisarc and suggesting comparison with the tesse- 
lated siliceous armour of Mallomonas, though until their cytology 
has been elucidated their affinities must remain in doubt. 
In connexion with the Cryptomonads, mention may be made 
of two remarkable and somewhat aberrant Flagellate genera 
recently discovered by Scherffel,' the position of which in the 
scheme of classification above outlined appears to be doubtful. In 
one of these forms, Monomastix, there are two large laterally placed 
green chromatophores, each with a pyrenoid, and starch is formed ; 
the cell shows dorsiventral symmetry and there is a single terminal 
flagellum. The other genus, Pleuromastix, is also a dorsiventral 
form, but has brown chromatophores and produces oil and probably 
also leucosin; it too has a single flagellum, inserted laterally at the 
obliquely truncate anterior end of the body. Scherffel inclines to 
the view that Monomastix belongs to the Polyblepharidaceae, but 
Pascher (in reviewing Scherffel’s paper in Zeitsclir. f. Bot., Bd. 5, 
1913, p. 405) considers that its affinities lie rather with the 
Cryptomonads; both writers refer Pleuromastix, somewhat doubt¬ 
fully, to the Chrysomonads. The most remarkable character 
common to these genera, apart from the possession of a single 
flagellum (all hitherto described Cryptomonads and Chloromonads 
have two flagella, though one order of Chrysomonads, the 
Chromulinales, is characterised by a single flagellum) is the presence 
of peculiar structures somewhat resembling the trichocysts found 
in some Chloromonads (Rhaphidomonas, Merotricha) and Peridiniales 
(Polykrikos , see above) as well as in the Ciliate Infusoria. These 
trichocyst-like organs, especially well developed in the green form 
Monomastix, consist of a highly refractive outer layer and a less 
refractive central mass which on treatment with various reagents 
is protruded rapidly as a filament (in Pleuromastix usually as a 
distinctly tubular structure). According to Scherffel, the structure 
of these organs in the two new Flagellates confirms the suggestion 
put forward by Kiinstler that the peculiar granular organs found 
lining the gullet-like depression in the Cryptomonad body represent 
rudimentary trichocysts. Among the Ciliate Infusoria correspond¬ 
ing organs occur, in addition to more highly organised trichocysts, 
and it appears probable that in both cases structures of this kind 
are not always to be regarded as defensive organs but may be 
merely products of secretion. Apart from its possession of pyrenoids 
and starch, Monomastix might well be placed in the Chloromonads, 
but on the whole it would appear that both genera may be perhaps 
best classed provisionally among the Cryptomonads—as here 
treated, this is a somewhat varied and generalised one, with many 
divergent affinities. 
1 “ Zwei neue trichocystenartige Bildungen fiihrende Flagellaten.” 
Arch. f. Protistenk., Bd. 27, 1912, pp. 94-128. 
(To be continued). 
