tips of some of the branches become darker in colour 

 and partitioned off from the remainder of the filament 

 by transverse walls similar to that which limits the 

 entire plant. After a time these apices open and 

 permit of the escape of the contents which, when 

 free, are seen to have the form of ovoid green masses 

 furnished with minute motile protoplasmic threads 

 or cilia, usually distributed in pairs over the entire 

 surface. These bodies, known as zoospores, move 

 by the rhythmic wavings of their cilia and are able to 

 propel themselves through 

 the water for a short 

 time. At length they reach 

 a suitable situation, settle 

 down, lose their cilia and 

 become covered by walls 

 similar to those of their 



parents. After a period of FlQ 6 yaucheria. Forma- 

 restgerminationcommences, tion of sexual reproductive 

 when from the resting spore 

 there arises a colourless 

 and a green filament. The 

 former branches and takes root in the mud ; the 

 latter also branches, but less frequently, and gradually 

 elongates into a plant like that from which the zoo- 

 spore originally sprang. Here we have a case of 

 multiplication or reproduction, and since only one 

 part is concerned, i.e., the zoospore, it is spoken of 

 as asexual reproduction (compare p. 8). 



At other times, however, the " germ " which corre- 

 sponds to and, at that stage, superficially resembles the 

 resting zoospore, is produced in an entirely different 

 manner. From the side of the filament arise, close 

 together in many forms, two short projections, at 

 first somewhat like the beginnings of two ordinary 



organs : A, male ; B, fe- 

 male ( x 50). (After Olt- 

 manns.) 



