and the Flagellata. 649 
An attempt is made to indicate the ‘ grade ’ of evolution by 
position considered vertically, and a horizontal line is drawn 
across each phylum where it appears to come to an end. 
PROTOCOCCOIDEAE ( Wille emend.). 
I. Volvocaceae 
5. Protococcaceae 
Chlamydomona- 
deae 
Phacoteae 
Polyblepharideae 
Polytomaceae 
Volvoceae 
Sycaminae ? 
Endosphaereae 
Halosphaereae 
Characieae 
6. Hydrodictyaceae 
2 . Tetrasporaceae 
3. Chlorosphaeraceae 
4. Pleurococeaceae 
\ Chlamydomonas,Carteria,Sphaerella, 
( Chlorogonium 
Phacotus, Pteromonas 
Polyblepharis, Pyramimonas 
Polytoma, Chlamydoblepharis 
( Gonium,Stephanosphaera, Pandorina, 
( Eudorina, Plaeodorina , Volvox 
Sycamina 
| Endosphaera, Chlorochytrium, Phyl- 
{ lobium, Chlorococcum 
Halosphaera 
( Characium [Ophiocytium] [Scia- 
( dium] [Peroniella] 
i Hydrodictyon, Pediastrum [Coelas- 
| trum] [Sorastrum] 
i Chlorangium, Tetraspora, Radiofilum 
[Mischococcus], Chlorodendron 
[Dictyosphaerium] [Oocardium] 
Chlorosphaera 
j Pleurococcus, Scenedesmus, Raphi- 
I dium [Stichococcus] 
CONFERVOIDEAE. 
7. Ulvaceae 
8. Ulothrichaceae 
9. Chaetophoraceae 
10. Mycoideaceae 
13. Coleochaetaceae 
16 . Sphaeropleaceae 
Monostroma, Ulva, Letterstedtia 
} Ulothrix, Hormidium [Conferva] 
| [Bumilleria], Microspora 
( Chaetophoreae Stigeoclonium, Pseudopleurococcus 
< Chroolepidae Trentepohlia 
( [Phaeothamnieae] [Phaeothamnion] 
11. Cylindrocapsaceae 12. Oedogoniaceae 
14. Cladophoraceae 15. Gomontiaceae 
Section I. Chlorophyceae. 
The subdivision of this group which is generally observed 
is that employed by Wille, into Siphoneae, Confervoideae, 
and Protococcoideae. The first of these groups is a natural 
