THE PHYLOGENY OF THE GENUS BRACHIOMONAS 77 
Brachiomonas into the pool from the open sea. Such an occur- 
rence might account for the sporadic appearance of the species 
at this station, though it is much more probable that it is usually 
present in a resting state and that conditions were not favorable 
for the production of zoospores at the time of other visits to the 
station. A strange point is that, although careful examination 
of the specimens collected in the spring of 1907 shows them all 
to be like Bohlin’s type, as were also the few specimens found 
there in September, 1920, and abundant material from March to 
June and in September, 1921, only a few such individuals were 
found in the fall of 1919 (Fics. 1, 2), while most of the material 
showed a distinct difference in form (Fics. 8-16). This can 
hardly be interpreted as a mere seasonal variation. New mater- 
ial collected the last of February of the present season, from 
pools still coated with ice, consisted very largely of the new 
obtuse form, but after a week or more in the laboratory this 
form had mostly been replaced by individuals corresponding to 
Bohlin’s type, present only in small numbers at the time of 
collection. Whether this is a case of the new type actually 
giving rise to the standard type through reproduction, or merely 
an example of the regular succession of growth of different organ- 
isms familiar in collections of protozoa, is a matter calling for 
more extended observation. For the determination of the per- 
manent status of the new form, pure culture methods are highly 
desirable, but thus far I have been unable to grow Brachiomonas 
on seawater agar, which succeeds admirably with other chlamy- 
domonads of similar habitat. For the present it will be con- 
venient to discuss this divergent plant under the name 
BRACHIOMONAS SUBMARINA Bohlin, forma obtusa f. nov. 
This new form is entirely like Bohlin’s type in its genera 
shape; that is, it possesses a long posterior extension or horn 
and four shorter median arms directed backwards, often with 
depressions between them; the anterior portion might be roughly 
likened to the shape of an umbrella with four ribs. There is 
often a wedge-shaped beak through which the cilia emerge, 
though sometimes the apex appears merely rounded. The 
protoplast may fill the arms and posterior horn entirely (Fic. 8) 
or partially (Fic. 12) or not at all. The massive chromatophore 
may be equally variable; that is the protoplasm in the horn 
and in the arms may be all green, as also in the typical form 
(Fic. 2), or it may be colorless, sometimes appearing sharply 
