24 
Blackman and Tans ley. 
descent. The history of these is a history of the intercalation of a 
vegetative phase between two successive motile (Chlamydomonadine) 
generations, these motile phases being retained for reproductive purposes 
as zoospores and gametes; in the oogamous types the male gamete alone 
remains motile, and constitutes in the Archegoniate series the last 
remaining representative of the Chlamydomonadine cell. 
The co-existence within the limits of an undoubtedly natural genus 
of the most primitive form of gamogenesis (the conjugation of equal 
clothed gametes) with a gamogenesis which has the essential characteristics 
of true oogamy is also a feature of unique interest.] 
3 . Splice vella. Sommerf. 
Body of Chlcimydomonas-ty pe but with wall widely out¬ 
standing, connected by protoplasmic threads. 
Pyrenoids one, two or many. 
4 . Chlorogonium. Ehrenberg. 
Body elongate, spindle-shaped, with a very thin closely 
adherent cell-wall. Flagella 2 . Chromatophore not 
well defined, spongy with colourless protoplasm in the 
meshes. Pyrenoids five or more. Numerous con¬ 
tractile vacuoles distributed through protoplasm. 
First division-plane transverse. Conjugation of naked 
isogametes. 
5 . Cercidium. Dangeard, 1887 . 
Body as in Chlorogonium , but with only two pyrenoids, 
anterior and posterior to the nucleus. 
III. Polytomeae. 
Body as in Chlamydomonadeae, but colourless, and usually 
without chromatophore-stroma. 
Reproduction as in Chlamydomonadeae, hut division taking 
place during motile condition. Daughter individuals are facul¬ 
tative gametes. 
1 . Polytoma. Ehrenberg, 1831 . 
Body with a thin closely adherent or slightly outstanding 
cell-wall. 
2 . Chlamydoblepharis. France, 1894 . 
Body with a very thick outstanding wall, often pierced 
by larger or smaller pores. 
(to he continued). 
R. MadleY, Printer, 151, Whitfield Street, W. 
