EE VISED LIST OF MARINE ALGiE. 77 



Separation of pale green or colourless portions of the 

 protoplasm first of all takes place, followed by oblique 

 septation of the green central portion. One of the taper- 

 ing cells thus formed then grows outwards, forming a 

 pseudo-branch. The filament then separates into two 

 parts, the isolated portion fixing itself by means of the 

 pale thick- walled process, whilst the already attached part 

 is terminated by a tapering pale green or colourless fila- 

 ment. 



Two kinds of zoospores are formed, large and small. 

 The megazoospore is pear-shaped, with a long, tapering 

 hyaline tail, and a large, often distinctly knobbed, colour- 

 less but granular head, from the centre of which arise 

 four long flagella, which project at right angles and bend 

 backwards along the sides of the conical body when at 

 rest. When in motion all four flagella move together 

 with a paddling movement. The megazoospores are more 

 plentiful than the zoogametes. Their mode of development 

 is as follows : — A cell usually about the middle of a fila- 

 ment enlarges, the chlorophyll retreats to the centre, and 

 a broad, granular, colourless layer is seen lying nearest to 

 the w^all. Eadial segmentation then takes place, and the 

 chlorophyll again spreads outwards, still leaving, however, 

 a narrow outer portion colourless or only faintly green, 

 more difficult to see at this stage owing to the spores 

 being crushed against the wall by their rapid increase in 

 size. When ripe the cuticular layer of the cell- wall bursts, 

 and the entire inner wall, with the enclosed spores, escapes. 

 The inner wall speedily deliquesces and the spores are set 

 free. They move slowly, and after a time settle down on 

 some adjacent rough surface. I have watched them settle 

 on a sporiferous filament of Bangia fuscopurpiirea, and 

 observed the first stages in the development of new fila- 

 ments. In the course of examination of hundreds of 



