CHLOROPHYCE 173 
Chetophora and the remaining genera, is without 
gametes so far as has been observed, produces zoo- 
spores in the vegetative cells. These escape through 
a hole in the membrane of the cell, and of that 
of the host-plant as well. They have no red 
spot, and since no observation has been made of the 
number of their cilia or of their germination, &., it 
is quite possible that they may prove to be gametes. 
LEpicladia and Bolbocoleon possess also zoospores pro- 
duced in the ordinary cells; in the latter case, also, 
no observation of the number of cilia has been made. 
Acrochete, which has short upright branches 
arising from the creeping filaments, forms zoospores 
in the terminal cells of such branches as have no 
bristles. In Acroblaste, also, the terminal cells of 
the upright branches become zoosporangia. 
The Geographical Distribution is world-wide in the 
fresh-waters, and very insufficiently known in the 
sea. The species of Ulothriz are in great confusion, 
but one certain form, UY. implexa, is marine, and 
occurs in British seas. Only two species of Cheto- 
phora are marine (neither of them British), both of 
them in the Arctic sea. Bolbocoleon, Epicladia, and 
Entoderma are all small genera, and occur in British 
and neighbouring seas. Phaophila, Acrochete, and 
Acroblaste, also small genera, have not yet been re- 
corded on British coasts. There are a number of 
other genera, such as Clenocladus, which occur in 
brackish water, but are scarcely marine. 
