CHLOROPHYCE^E 173 



Chcetophora 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, &c., it 

 is quite possible that they may prove to be gametes. 

 Epicladia and Bolbocolcon possess also zoospores pro- 

 duced in the ordinary cells ; in the latter case, also, 

 no observation of the number of cilia has been made. 

 Acrochcete, 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 

 jbh^ upright branches become zoosporangia. 



The Geographical Distribution is world-wide in the 

 fresh-waters, and very insufficiently known in the 

 sea. The species of Ulothrix are in great confusion, 

 but one certain form, U. implexa, is marine, and 

 occurs in British seas. Only two species of Chceto- 

 phora are marine (neither of them British), both of 

 them in the Arctic sea. Bolbocoleon, Epicladia, and 

 Entodcrma are all small genera, and occur in British 

 and neighbouring seas. Phceophila, Acrochcete, and 

 Acroblaste, also small genera, have not yet been re- 

 corded on British coasts. There are a number of 

 other genera, such as Ctenocladus, which occur in 

 brackish water, but are scarcely marine. 



