THE PHYLOGENY OF THE GENUS BRACHIOMONAS 79 
could be modified or suppressed after they are once formed; 
nevertheless in practically all examples of division seen, I have 
found the arms well developed before the escape of the daughter 
cells (FIGs. 20, 21) so that such cells can hardly be looked upon 
as a reversion to the simpler ancestral form. 
. The main difference between this new form and Bohlin’s 
type lies in the fact that the arms are here always rounded and 
obtuse, while in the type form they are sharp pointed and often 
more eae The characters of the form may be summarized 
as foll 
BSACHibEnNad SUBMARINA Bohlin, forma obtusa f 
et chromatophoro alias i in extrema ipsa extendentibus, alias ex 
eis plus minusve retractis. 
Longit. cellularum 15-32 (saepius 20-25,); lat. cell, 15- 
22u (saepius ca. 18,). 
Hab. in aquis subsalsis lacunarum saxearum. Twin Island, 
Pelham Bay, New York; Nov., 1919, Feb.—March, 1922. 
Chodat’s figures (2, f. 66) indicate that the form collected 
in Corsica may be identical with the one here described, though 
it is possible that the difference between his sketches and those 
of Bohlin may be due to the personal equation in drawing. 
As indicated above, I have found this obtuse form only at 
one station. Bohlin’s type, as represented by my FIc. I-55 
have also collected early in September during each of the past 
two years at Bass Point, Nahant, Massachusetts. It should 
be looked for on the coast of Maine and New Brunswick as 
well, at any points where rocky ledges occur. 
In older cultures numerous cells were found which showed 
the entire protoplast contracted into a globose mass (FIG. 16). 
These showed no further development in this material; but in 
fresh hanging drop cultures of B. submarina followed for a much 
shorter time in Norway, such cells presently became quiescent 
and developed a new spherical wall closely investing the pro- 
toplast. Soon these aplanospores showed their chromatophore 
turning ‘from green to a tawny tint, and finally the original 
wall of the zoospores gradually disappeared. 
Practically all genera allied to Chlamydomonas possess two 
contractile vacuoles pulsating more or less in alternation, 
situated near the base of the cilia. In Brachiomonas these 
appear to be entirely absent. One of West’s figures (12, pl. 20, 
f. 1; 14, f. ror c), it is true, suggested such vacuoles, but his 
