80 THE PHYLOGENY OF THE GENUS BRACHIOMONAS 
beautiful original sketches in color, preserved with his collection 
of drawings in the South Kensington Museum, show that these 
spots are brown colored granules suspended in the fluid of a 
large permanent vacuole. The absence of contractile vacuoles 
I have been inclined to regard as another mark of the highly 
specialized character of the genus, since they are regularly to 
be expected in primitive members of this group and its ancestors. 
It is possible, however, that this peculiarity is merely an incident 
due to the special habitat; for Biitschli has remarked the general 
absence of contractile vacuoles in marine Ciliates and Rhizopods, 
and D’Arcy Thompson (11, pp. 165 and 264) regards this 
absence in such cases as ‘‘no more than a physical consequence 
of the different conditions of existence in fresh water and in 
salt.”” The marine species, Chlamydomonas brachyura West, 
besides exhibiting other points of resemblance to Brachiomonas, 
appears also to have no contractile vacuoles; this species was 
discovered in association with a new Carteriaceous genus 
Platymonas, in which West (13) found two small contractile 
vacuoles, which, however, ‘‘could only be observed with dif- 
ficulty.”” In two brackish water species of Platymonas which 
I have investigated with considerable care, I am unable to 
satisfy myself that I ever see contractile vacuoles. Lewis has 
just published figures of one of these species, P. subcordiformis 
(Wille) Hazen,* which likewise show no contractile vacuoles. 
Furthermore, two new brackish water forms of the primitive 
family Polyblepharidaceae, one a minute species of Pyramimonas 
and the other a new genus most closely related to Polyblepharides, 
which have turned up in my latest collections of Brachiomonas, 
made while this paper was in the hands of the printer, very 
certainly possess no contractile vacuoles. Over against these 
several records of their absence, however, attention may be 
called to their presence (though here very small) in Chlamy- 
domonas caudata Wille, discussed below, which must be con- 
sidered as regularly a marine organism. 
Asexual reproduction is accomplished by internal division 
into four or eight (very rarely perhaps two) daughter cells. 
The division very generally begins while the cell is swimming 
actively, and often the typical cell shape is acquired by the 
daughter cells or zoospores and they move with their own cilia 
inside the mother cell-wall while it continues in active movement 
* Notes from the Woods Hole Laboratory,—1921. Platymonas subcordi- 
formis (Wille) Hazen, Rhodora 23: 249-251. pl. 133, f. 1-19. Mr 1922 
