22 
Blackman and Tansley. 
Reproduction, either only by vegetative division usually into 2 , 4 , or 
8 daughter individuals, or more commonly also gamogenetic by the 
isogamous union of planogametes, produced similarly to the vegetative 
daughter individuals, but in greater numbers, rarely by the hetero- 
gamous union of planogametes or by oogamy. 
The first cell-division-plane is typically transverse to the long axis of 
the cell. 
[The vegetative division in this family which gives rise at once to 
new motile individuals is strictly comparable with the formation of non¬ 
conjugating swarmers (asexual reproduction by zoospores) in the other 
classes of Green Algae.J 
[The coenobium is a special type of the aggregation of cells to form 
a colony, characterised usually by its high integration, and by the 
fact that no increase in the usually quite definite number of cells takes 
place after birth, but all the cell-divisions occur in the embryo while 
inside the mother-coenobium and all the resulting cells belong typically 
to the same generation.] 
[According to modern views the Green Algae are derived phylogen- 
etically from the Flagellata, a group of unicellular organisms usually 
reckoned by zoologists as belonging to the Protozoa and containing 
a very varied assemblage of forms, many of which shew a mixture of 
animal and plant characters. The Volvocaceae naturally connect the 
Green Algae with the Flagellata, and on account of their motility and 
the general resemblance of their body to the Flagellate type are often 
included in the latter group. Klebs (1892) 1 however showed that a great 
consensus of characters united the Volvocaceae with the Green Algae, and 
separated them from all other organisms of the Flagellate type, and the 
case for their separation is in our opinion overwhelming. It will be 
convenient to insert here the characters of the Flagellata as distinguished 
by Klebs, for comparison with the diagnosis of the Volvocaceae given 
above. 
Flagellata. Body unicellular or a colony of cells, cell uninucleate 
with a thick or thin external layer of protoplasm the periplast in which 
amoeboid changes of form may take place. Outside this a non-living 
investment of the cell is frequently present; it may present the most varied 
form and is often not closely adherent to the body. Specialised anterior 
end of clear protoplasm bearing one or more flagella. One or more 
contractile vacuoles are present. Organism always remaining capable 
of movement. Nutrition either holozoic (solid food being taken by 
pseudopodia, through a specialized mouth, or otherwise), saprophytic or 
holophytic. In the last case the chromatophores are green or yellow and 
may take the form of bands , plates or discs. True pyrcnoids entirely 
absent. Paramylon, leucosin or a fatty oil the visible anabolites. 
Starch entirely absent. Reproduction by simple longitudinal division , 
usually beginning at the anterior end of the body. Individual always 
capable of forming resting cysts. Gamogencsis apparently entirely absent.'] 
Sub Family I. Polyblepliarideae. 
Body unicellular of varied shape without cell-wall, capable 
of some change of form. Flagella four (rarely more). Typical 
Volvocine chromatophore, pyrenoid and eyesfot. Reproduction by 
longitudinal division. Gametes unknown. Resting cysts formed 
directly from motile individuals. 
[.Special interest attaches to this family since it clearly exhibits a 
mixture of Flagellate and Volvocine characters.] 
1 Klebs. Flagellatenstudien. Zeitschr.f. zviss. Zool, 1891 . 
