1899] BRIEFER ARTICLES 313 
cells, before any other division had occurred (jig. 75). These zoo- 
spores were not seen to be liberated, but they appeared to be perfect, 
as each showed distinctly an eye-spot. 
In the thallus the zoospores are generally formed in the thickened 
portion near the center and rarely near the edge. Often the whole 
center of the thallus has produced zoospores, leaving the cells perfectly 
eupty, and many individuals were noticed on the side of the glass 
that were ring-shaped, as if the center were entirely gone. 
Whereas in most other algze which reproduce by means of zoospores 
these are usually formed when transferred from nutritive solution to 
water, or from stronger nutritive solution to weaker, or from agar cul- 
‘ures to liquid, in this species they are formed when the thallus is 
subjected to any sudden change. As might be expected, they are pro- 
duced when the disc is transferred from agar to Knop’s solution, but 
they are also produced when transferred from water to Knop’s solu- 
ton, and when transferred from water to agar. They may be formed 
within twenty-four hours after these changes are made, but often they 
do not appear until the second day. In some cases nearly the whole 
thallus was seen to produce zoospores. 
Alter repeated attempts to find the principles governing the pro- 
duction of the zoospores, no results were obtained farther than that, 
chang limits, the greater the change of conditions the greater 
€r of zoospores and the sooner their formation. 
ee this alga greatly resembles Coleochete in sage 
ied oe Ee over organization. Its well developed is sot 
Cleschste mag inherent in the alga, as in Pediastrum or - pit 
conditions , py erently is due only to contact, for, whatever t Kobe : 
solid Seta be, it cannot be made to assume this form wl 
atum. 
The fact 
Sho differe 
fu 
it 
that it so easily reverts to a unicellular state in which there 
Octions f tag of cells, but each is capable of carrying whee 
 elaaeeat and the fact that zoospores may arise directly 
ttl eid zoospores, show a development but little Ay i 
organisms cellular forms. It may possibly be regarded as a aa 
© lower 2 Ebi wa little known, which are transition forms a ot 
°F the ee 2 higher algze, and may assume the nature of 
That it engaged to external circumstances. eooee 
"Xplained s been found under conditions so very unlike 1s és 
“and the fact that it has been so rarely found, and then 1 
