and the Flagellata . 677 
cilia are clearly seen, but if killed with osmic acid (Fig. 14, d ), 
the short one curls back tightly against the body, and is 
invisible. After a few hours’ swarming the zoospores come 
to rest, secrete mucilage round them, and begin dividing to 
form a new colony. There is no sexual reproduction. 
The relation of Chlorosaccus to Chloramoeba seems clear. 
Its Tetraspora-\i\ze aggregation and the shortness of the 
motile stage are plant characteristics, while its incomplete 
wall and absence of sexual reproduction are Flagellate charac¬ 
teristics. Luther, attaching much importance to the vegetative 
division being parallel to the long axis of the cell, allows 
this to weigh down the balance and classes it as a Flagellate 
in the same family with Vacuolaria ; but it seems to me that 
he overrates the importance of this, since Dill has shown 
that the lower Chlamydomonads divide in this way, and as 
division must go so if the colony-membrane is to expand 
tangentially without cell-displacement. Perhaps then it may 
be ranked as an Alga rather than a colonial Flagellate. At 
all events it is very nearly balanced on the line between the 
two classes, and only serves to illustrate the absence of 
absolute cleavage-lines and how in a difficult case one’s 
decision may almost be called ‘subjective.’ 
The great stumbling-block in the way of deriving the Con- 
fervales from a Chlorosaccus type, just as the Confervoideae 
are derived through a Tetraspora type, was obviously the 
difference in the ciliation of the zoospores. 
The zoospores of the typical genus Conferva have several 
discoid yellow-green chloroplasts, as analogy would indicate, 
but they are described by Klebs and other good observers 
as having only one cilium—a long one. Luther made the 
important discovery that they really have a second short 
cilium, and if they have been killed with iodine this can be 
seen standing out from the body (Fig. 14 ) d). Most fixing 
reagents, however, cause this one to curl back against the 
body and to become invisible. He found also that just the 
same holds good for Botrydiopsis, another genus of the Con- 
fervales which he investigated. This character then appears, 
