21,2 Shaw: Copelandosphaera 227 
adapted to this end. There is reason to believe that, as was 
pointed out by Powers (’08 p. 170), European workers have 
encountered in their own region species that have not received 
due recognition until found elsewhere. 
My present view, in December, 1921, of the relationships of 
Copelandosphaera is indicated by the diagram of the phylogeny 
of the Volvoceae given in fig. 2. The broken line from Stepha- 
nosphaera to Volvox is a reminder of the view advanced by Crow 
(18) that Volvox and Janetosphaera are allied to Sphaerella 
rather than to Chlamydomonas. According to his view the 
species shown here should be represented as forming two genetic 
trees instead of one, 
KEYS TO THE GENERA AND SPECIES OF THE SUBFAMILY VOLVOCEAE 
Key to the genera. 
1. Coenobium a plate of biciliate cells. 
2. Cells all facing with one side of plate............... Gonium. 
2. Some cells facing with each side of plate Platydorina. 
1. Coenobium globose, ellipsoidal or ovoid. ; 
2. Cells on equatorial belt, facing outward Stephanoon. 
2. Cells in entire surface of spheroid. 
3. Cells all alike. 
4. Inner sides of cells pyramidal Pandorina. 
4. Cells globose , aes Eudorina. 
3. Vegetative cells differentiated. 
4. No vegetative cells in reproductive area.......: Pleodorina. 
4. Vegetative cells in reproductive area. 
5. Gonidia differentiated after birth Besseyosphaera. 
5. Gonidia differentiated before birth. 
6. No intercellular protoplasmic strands. 
7. Gonidia not differentiated in young embryos. 
Copelandosphaera, 
7. Gonidia differentiated in young embryos; becoming very 
large. 
8. Gonidia not migratory in embryos........ Merrillosphaera. 
8. Gonidia migratory in embryos............... Campbellosphaera. 
6. Cells connected by intercellular, protoplasmic strands, 
7. Cells round; without separate inner walls.... Janetosphaera. 
7. Cells stellate; with separate inner walls................. .. Volvox. 
Key to the species. 
GONIUM 
1. Cells 16 G. pectorale Mill. 
1. Cells 4. : 
2. Cilia vibratile throughout. : .. @ sociale (Duj.) Warm. 
2. Cilia vibratile only in terminal half... G. lacustre West. 
PLATYDORINA 
Cells 16 or 32, arranged in a horseshoe-shaped plate, those of the two faces 
intercalated; posterior end with 3 or 5 tails.............. P. caudata Kofoid. 
187897-——7 
