220 
Blackman and Tansley. 
cell-contents to form a number of spherical aplano- 
spores or a larger number of zoospores. The 
zoospores have been proved to possess two lateral 
chromatophores and two unequal flagella. The 
aplanospores may become zoosporangia or, after 
resting, gametangia. The gametes are described as 
having a single chromatophore and two approximately 
equal flagella. 
3. Ophiocytium. Nageli, 1849. 
Cell sub-coenocytic free or attached, cylindrical, straight, 
or spiral, containing several nuclei and several large 
parietal chromatophores. No vegetative division 
occurs. Reproduction by division of the contents 
to oval aplanospores or to eight zoospores which 
are liberated by the splitting-off of the upper end of 
the cell as a lid. In the attached species the lower 
part of the cell remains as an empty open tube, on 
the rim of which the zoospores come to rest and 
develop as a whorl of new tubes. Repetition of this 
generates a polytomous branch-system of empty 
tubes. Existence of gametes uncertain. 
4. Conferva. Lagerheim, 1888. 
Cells with one or two nuclei, and several chromatophores; 
united to form uniseriate filaments. Reproduction 
by the formation of oval aplanospores or by zoospores 
(one or two from each cell), provided with one long 
and one very short flagellum and a number of discoid 
chromatophores. Zoospores escape by the cells split¬ 
ting cleanly across at the middle. A long filament 
may thus split up to a number of so-called H-pieces. 
The gametes are all alike and of the same appearance 
as the zoospores, yet they conjugate anisogamously, 
one coming to rest and rounding up before another 
swarms up to it and fuses with it. 
[The very special structure of the cell-wall common to these two 
genera unites them closely together. The H-pieces of Conferva are 
made up of a number of apposed layers of pectic compounds, which 
can be distinguished by staining. The Ophiocytium cell is to be 
regarded as made up of a small homogeneous lid closing a long tube 
which has the structure of half such an H-piece.] 
5. Bumilleria. Borzi, 1895. 
Closely resembles Conferva in life-history and in 
appearance, but the H-pieces do not apparently 
possess the same special structure and do not divide 
the cells sharply into halves. More than two zoospores 
may arise in one cell. Nature of gametes uncertain. 
(To be concluded.) 
tt, MAULEY, Printer, 151, Whitfield Street, W. 
