THE MAIN LINE OF DESCENT THROUGH THE GREEN ALG. 39 
line leading to and ending in Volvox—the highest form that 
could evidently be produced by a Chlamydomonas type which 
could not give up its motility. However, it is from the 
palmelloid condition that the greatest developments have 
arisen, and a little consideration will show that there are so 
many directions along which advance can be made by a non- 
motile organism that many complications may be expected. 
This is found to be so, there being many side branches from 
the main line leading to special developments that have ended 
blindly by becoming highly specialised. A group of forms 
(1) Diagrammatic representation of Chlamydomonas: Chl, Chloroplast, n, nucleus, 
e, eye-spot, v, contractile vacuoles, p, pyrenoid ; (2) Chl. Kleinii Schm., from Bowling ; 
(3) Chl. Braunii Gor, palmella condition (after Lotsy), evidently showing vegetative 
division ; (4) Palmodactylon varium Nag, from Glen Falloch, (a) from Strathblane (both 
diagmc.); (5) Tetraspora gelatinosa (Vauch.) Desv. (diagmc.) from Gourock ; (6) Hor- 
mospora (sp.?) from Strathblane; (7) Hormospora mutabilis, Bréb., from Bute; (8) 
Ulothrix zonata (Web. et Mohr.) Kiitz., (a) microzoogonidium, (b) macrozoogonidium ; 
(9) Cheetophora incrassata (Huds.) Hazen, from Possil. (Small portion from end of a 
branch); (10) Outline of portion of a species of Coleochzte, from Strathblane ; (11) 
Portion of thallus of Coleochete scututa Bréb., from Bardowie Loch. 
known as the Palmellaceze is readily derivable from Chlamy- 
domonas, in fact it might almost be said they are non-motile 
Chlamydomonads, z.e., non-motile in the main, for in reproducing, 
zoospores and gametes recalling in detail those of that uni- 
cellular genus are formed. In Tetraspora (fig. 5), which forms 
large gelatinous masses in pools, etc., and is fairly common in 
“Clyde,” there is a tremendous vegetative increase by division 
of cells, usually into fours, but eventually motile cells harking 
back to the primitive type are produced for reproductive 
purposes. The line of development under consideration is 
usually spoken of as being due to the ‘‘tetrasporine tendency ” 
