Flagellata and Primitive Alga. 
111 
the vegetative and the reproductive cells and more marked oogamy, 
the oogonial cells being differentiated at an early stage in the form¬ 
ation of the ccenobium and having no flagella. Van Tieghen’s genus 
Scyamina is an imperfectly known colourless form, in which the 
numerous cells are placed at different depths in the spherical 
coenobium, instead of being confined to the periphery as in Eudorina; 
it is quite uncertain whether it represents a saprophytic offshoot 
from a Eudorina-like type, or a form derived from Polytoma by 
coenobial development, or indeed whether it is rightly placed in the 
Volvocales at all. 
The inter-relationships of the Volvocales, as here suggested, 
are indicated on the accompanying Table B. 
VI. —The Chrysomonads. 
Since the publication of Senn’s compilation in 1900, much work 
has been done on the Flagellate forms included by him in the 
Chrysomonadineae and Cryptomonadineae. From the extensive re¬ 
cent literature of these forms, to which Pascher has been the largest 
contributor, it will suffice to select for mention certain results which 
are of special interest in connexion with the phylogeny of the Algae. 
Various new genera have been added to those enumerated by Senn, 
and some modifications of the earlier classification have been 
suggested. Senn divides the Chrysomonadineae into three families 
characterised respectively by the possession of a single flagellum 
(Chromulinaceae), two equal flagella (Hymenomondaceae), and two 
unequal flagella (Ochromonadaceae). Scherffel (125) has shown 
that Monas, Oikomonas, and various other genera placed by Senn in 
the Protomastigineae are better regarded as colourless forms derived 
Chrysomonads; for instance, they show precise agreement with 
normal coloured Chrysomonads in producing leucosin, in the mode 
of encystment, and in various cytological details. In describing a 
new species of Gymnodinium, a genus belonging to the simpler 
Peridiniales which have been regarded as derived from the Chryso¬ 
monadineae (see below), Ohno (94) criticises the systematic value of 
the flagellum number in the classification of the Flagellata. This 
new species differs from all other Peridiniales in having two longi¬ 
tudinal flagella instead of one, in addition to the usual transverse 
flagellum, but otherwise must be placed in the genus Gymnodinium. 
The same objection has been raised with regard to the lower Green 
Algae, 1 but Senn’s classification is accepted by Pascher and other 
recent writers on the Chrysomonads, since (as in the case of the 
Green Algae) the groups are distinguished by characters other than 
the number of flagella. In Pascher’s suggested classification (99), 
the Cryptomonads are merged in the Chrysomonadineae, which are 
divided into four orders. The first three of these (Chromulinales, 
Isochrysidales, Ochromonadales) coincide with Senn’s three families 
of Chrysomonadineae, while the fourth (Phaeochrysidales) is charac¬ 
terised by the possession of laterally inserted flagella—in the other 
three orders the flagella are terminal—and includes the Crypto¬ 
monadineae of Senn. 
l,See Review of Wille’s classification of Green Algae, by R.P.G., New 
Phytologist, vol. IX., 1910, p. 78. 
