259 
Notes on Freshwater Algce . 
Oedogonium a having as crown of relatively short cilia. Published 
figures generally show the cilia about J to J as long as the body of 
the zoogonidium. The length of the cilia of the zoogonidia of O. 
cryptoporum (Fig 1, G), however, were observed to be § to \ of 
the body-length, as the measurements given below show. 
The zoogonidium of O. cvyptoporum is oval or subellipsoid in 
shape, with a prominent hemispherical and hyaline anterior papilla. 
Fig. 1, G shows the position the cilia always assume when the 
zoogonidia are killed with a drop of dilute iodine solution. The 
following are a few measurements of the length of cilia and length 
of body of the zoogonidium (including the anterior papilla). 
Body-length 22-5 | 20-0 | 19-7 | 20-0 \ 2F5 | 200/* 
Length of Cilia 15*8 | 15-5 j 14-0 | 16*0 | 15 5 | 15-2/* 
The relative length of these cilia appears to be markedly 
greater than that recorded in the motile cells of any other member 
of the Oedogoniales, as far as can be ascertained from published 
figures. 
The zoogonidia of this species have no eye-spot and are 
negatively phototactic, always accumulating on the side of the 
culture-vessel which is turned away from the source of light. 
The mode of progression is rather interesting and is represented 
by Fig 1, H. The arrow gives the general direction in which the 
zoogonidium is moving, but the longitudinal axis of the latter is 
never parallel to this direction but makes an angle of about 22*5 9 
with it. Observed under a low magnification the anterior end of 
the moving zoogonidium appears to oscillate from side to side, but 
in reality the anterior end describes a circle, the direction of its 
motion (the zoogonidium being considered as moving towards the 
observer) being anti-clockwise. In other words the longitudinal 
axis of the zoogonidium describes a cone, the apex of which is the 
extreme posterior end of the zoogonidium while the axis of the 
cone gives the actual direction in which the zoogonidium is moving 
as a whole. 
Occasional zoogonidia of several other (undetermined) species 
of Oedogonium and Bulbocluzte have been seen at various times, but 
the relative length of their cilia was always observed to be very 
much shorter than is the case with those of O. cryptoporum. 
Doubtless, however, this species does not stand alone in having 
zoogonidia with rather long cilia. 
