THE PHYLOGENY OF THE GENUS BRACHIOMONAS 89 
ways preceeded, in his opinion, by a rotation of the protoplast, so 
that he believes the manner of cell division to have no phyloge- 
netic significance. Attractive as this view is in its possibility of 
simplifying the idea of direct transmission of polarity to the 
daughter cells (and my own recent studies on Chlamydomonas 
somewhat tend to support such a view) nevertheless we still 
lack sufficiently definite and accurate observations to permit 
the denial that an actual transverse division may occur in some 
species. 
If in C. caudata the first cleavage plane is actually or by 
rotation of the protoplast transverse (as appears to me most 
probable), and if we accept the current view derived from Dill 
(4) that the most primitive species are those in which both 
divisions are longitudinal, then C. caudata could hardly be re- 
garded as an actual transitional form between the ordinary 
ovoid Chlamydomonas type and the Brachiomonas group, since 
all species of the latter genus appear to have retained the primi- 
tive mode of division by two strictly longitudinal cleavages, 
in spite of their advancement in other respects. evertheless, 
in its general morphology, and in the similarity of its method of 
formation of aplanospores (rarely found in other species of 
Chlamydomonas), C. caudata must be very close to the ancestral 
line which has given rise to the four forms of Brachiomonas 
recognized above; and these present a rather close ascending 
series, with perhaps a definite orthogenetic tendency beginning 
with B. simplex, which is barely emerging from the Chlamydo- 
monas stage, through B. submarina f. obtusa and then B. sub- 
marina (type) to B. gracilis, an extremely slender form, so far 
removed from any Chlamydomonas type as to justify thoroughly 
the retention of Brachtomonas as a genus. 
In certain graphic schemes of the phylogeny of the chlamydo- 
monads—e. g. those of Wille (15) and West (14, p. 163)—the genus 
Lobomonas Dangeard is indicated as representing an inter- 
mediate stage between Chlamydomonas and Brachiomonas; but 
the two known species of Lobomonas, as well as two new species 
to be described by the writer in the next number of this journal, 
are very minute forms, and in their general morphology exhibit 
by no means so good a connection as is shown by C. caudata 
and B. simplex. Lobomonas must be regarded as a special 
offshoot from the Chlamydomonas line not leading to anything 
higher, so far as we know at present. 
ARNARD COLLEGE, 
CoLUMBIA UNIVERSITY 
