Fresh-Water Algce of Canada. 459 



the plant and not necessary to its fecundation. In a few in- 

 stances we have seen the sporangia very distinct, but only 

 in a few. For the most part the spores, or zoospores, contained 



Fig. 6. Z. catenceforme, in conjugation. 



in the spiral threads, becoming diffused through the cells 

 break the walls and escape into the water. This simple process 

 seems to be the one most commonly followed. If fertilization 

 only takes place through the ao-ency of sporangia and by the zoos- 

 pores which it contains, or only by the action of the cytoblast, the 

 plant, according to our observation for now two years, would soon 

 altogether disappear. Apparently, however, without the con- 

 jugation of adjacent cells, or of cells of adjacent' filaments, and 

 without the cytoblastic organ, spores or zoospores are formed 

 and, escaping from the cells, immediately become fertile. From 

 the facts which have come under our observation we are tempted 

 to think that the union of cells is purely accidental, and results 

 from the process of endosmosis, or by simple attraction. We are 

 the rather confirmed in this conjecture by the fact that conjuga- 

 tion takes place chiefly in spring when life is most active and the 

 membranes of the cells most delicate. The intrusion of the new 

 matter into a cell may also under such conditions result in the for- 

 mation of new cell membranes ; and the occasional reddish color 

 of the sporangia may be merely the effect of age. Not having 

 seen the cytoblastic organ we can form no conjecture as to its 

 function, bnt the fact that it is of so rare occurrence naturally 

 leads to the inference that it is an accidental excess of mucous in 

 the cell and by no means necessary for the fertilization of the 

 spores. Hassall himself admits " that this combination (conjuga- 

 tion) is not an essential to the perpetuation of the species " ; but 

 he does this on the ground that the cytoblastic organ is that 

 which fertilizes the zoospores, and thinks that by this means 

 the permanence of species is explained where cells have broken 

 up " before the union of endochrome, or the formation of spores, 

 has taken place." But, allowing this to be the case, how again 

 shall we account for the permanence, or the reproductive germs, 

 of those species in which there are neither cytoblastic organs, 



