VARIATION IN THE DESMIDIEE. 409 
1 append the following table to illustrate this point :— 
M.CR)x = MELITENSIS Hass 
M, DEPAUPERATA NORDST | M Crux=Meuitensis vaRS.( Bonge 4 Gutw) 
M, RABENHORSTII var.Tatrıca Racıa 
M,DEPAUPERATA FORMA West KG.S.Wtsr | " 
M.RagENuORSTIi Kircun, 
M,OSCITANS VAR MUCRONATA FORMS (Cooke Xe) 
` M,PINNATIFIDA VAR. DIViSA West. 
M,OSCITANS VAR MUCRONATA WILLE. 
M,PINNATIFIOA VAR. EXPANSA TURNER. 
M,PINNATIFIDA VAR, INFLATA WOLLE. 
M,LATICEPS Norost LUN == = /. M,incisa Dnta. 
. 5N 
[ M,OSCITANS Murs, | M.PINNATIFIOA RALFS | 
` / 
N _ 7 
— ee - Jo. 
| M,ARCUATA VAR SUBPINNATIFIDA West X GS WEST, 
| M.ARCUATA Bait 
M.ARCUATA VAR EXPANSA NonpsT. 
M.ARCUATA VAR Gracitis West & G.S. Wesr 
I can find only one paper dealing with the question of the 
general evolution of Desmids, and that by Bougon *. In it he 
attempts to show by means of a “ Généalogie des Desmidiées 
(de bas en hiut)” that the Desmicie® were originally derived 
from the Infusoria Flagellata, and that the maximum degree 
of specialization has been reached by Hyalotheca dissiliens ! 
Altogether it is a production testifying to the scant knowledge 
of the author with regard to the Desmidiex in general. In the 
first place, L think it has been almost conclusively proved t that 
the Desmidiew are a degenerate family of Alge which have 
originated from filamentous conjugates by loss of the filamentous 
condition t, accompanied by the development of specialized 
morphological characters. It is a notable fact that Desmidium 
* Bougon in ‘ Le Micrographe Préparateur,’ vol. v. no. 2, 1897, p. 67. 
+ West & G. S. West, “ Obs. on the Corj.," Ann. Bot. vol. xii. March 1898. 
+ This has been again acquired by about eight genera and several individual 
species of other genera. 
