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P. C a vet's 
pharidaceae—may well have arisen from a common ancestral form, 
which we may imagine to have been multiflagellate and amoeboid, 
with a basin-shaped chromatophore. Apart from the differences 
in flagellum number and the nature of the assimilate we fiind corres¬ 
ponding simple “ mastigamoeboid ” forms in each of the orders of 
Chrysomonadinese—e.g., Chrysamceba, Hymenomonas, Ochromonas, 
Wysotzkia ; while the Chloromonad genus Chloramceba suggests the 
origin of the Chloromonadineae from a similar ancestral form by 
the division of the primitively single basin-shaped chromatophore 
into a number of small chloroplasts. If the multiflagellate condition 
is taken as primitive, we must regard the Polyblepharidaceae, which 
also have a limited power of change of shape, as being nearer to the 
ancestral stock than any of the other coloured Flagellate and lower 
Algal forms. 
The nearest approach to such an ancestral form is the colourless 
Multicilut, with two species, of which M. lacustris is multinucleate 
while M. marina has a single nucleus ; in both species, the spherical 
body bears numerous radiating flagella, food is ingested by 
pseudopodia which may be put out from any point, there are numerous 
peripheral contractile vacuoles, and division occurs by median 
constriction of the body as in Amceba. Probably the primitive form 
of chromatophore was a reticulate peripheral sheet immediately 
within the periplast, and when the flagella became restricted to the 
anterior end of the body this sheet would become basin-shaped 
(i.e ., open anteriorly) as in the majority of Volvocales and in various 
Chrysomonads, or on the other hand broken up into numerous small 
chromatophores, as in Chloromonadinese, Glceomonas (allied to 
Chlamydomonas), Chrysococcus dokidophorus (Chromulinales), etc. 
A reticulate chromatophore occurs in Chrysapsis (one of the most 
primitive Chrysomonads), and in certain Volvocales ( Sphcerella , 
Chlorogonium). The bell-shaped chromatophore which is character¬ 
istic of the Volvocales and of the simpler Chrysomonadineae has 
undergone longitudinal splitting in at least one genus ( Scherffelia ) 
in the former group and in the majority of the Chrysomonadineae, 
giving rise to two lateral curved band-like chromatophores; these 
two types of chromatophore may occur in different species of the 
same genus, as is seen in Uroglenopsis (Ochromonadales). 
If, while bearing in mind Vuillemin’s timely caution against 
dogmatism in such matters, we assume that autotrophic organisms 
are primitive and heterotrophic organisms derived, and that the 
Flagellata represent the most primitive organisms known to us, the 
striking parallism which has been shown to exist between the Brown 
Flagellates and certain colourless Flagellates suggests the view 
that the whole of the latter may have arisen from coloured autotropic 
forms by adaptation to heterotrophic modes of nutrition. On this 
view, the classification of the Flagellata which has hitherto been 
accepted is purely physiological, and therefore artificial, correspond¬ 
ing with the conventional division of the Thallophyta into Algae and 
Fungi; and the various groups of colourless Flagellates will doubtless 
be shown, on further investigation, to have arisen from correspond¬ 
ing forms among the coloured Flagellates, just as the various groups 
of Fungi are now regarded as arising from corresponding Algal 
forms. Of the many lines starting from a hypothetical autotrophic 
Multicilia-like ancestral form, with a reticulate chromatophore, 
