116 
no other author before Ralfs has taken it in so 
restricted a sense as he. 
That Cor da’s figg. 64 and 65 in Aim. d. Carlsb. 
1835 t. 5, which Ralfs probably had not seen, 
do not belong to the same species as CL didymotomm 
Ralfs in Br. Desm., is evident; but Corda’s figg. 
come very near to Delponte’s Cl. Hirudo. It seems 
very dubious, if Cl. directum Bréb. 1835, quoted by 
Ralfs as a synonym, be identical with Ralfs Cl. 
didymotocum. Cl. Ensis Focke 1847 is not taken up 
as species name, although identified with Cl. didymo¬ 
tocum Ralfs by several authors. Therefore it is 
best, to keep the name dost, didymotocum^ but with 
Ralfs as author. 
Echinella acuta Lyngbye 1819 is according to 
Heiberg’s examination — lacustris and Sy- 
nedra fascicularis. The first author, who had in view 
a true Closterium with this name, is Corda in Sturms 
Deutschl. Flora II. 18 n:o 15 fig. A. et B. A re¬ 
viewer in Literaturber. z. Linnæa 1832 said about 
these figures: ”Grut, aber grün?” Yes, they are green, 
as they should be. 
From the preceding it will be seen, that during 
a long time a great uncertainty prevailed as to the 
definition of species, genera and families, and that 
there could be reasons for the replacing of a few 
species in Ralfs’ Brit. Desm. by earlier names, and 
many more species, if our claims upon identity are 
very small. Also for the resurrection of some older 
genera more or less valid reasons could be found out. 
In my opinion it is best for the stability of no¬ 
menclature to start from Ralfs’ British Desmidieæ 
1848 with no emendations or with as few as pos¬ 
sible. As shown above, I consider no substitution of 
Ralfs’ generic names by any older ones advisable. 
But of course some of Ralfs’ genera must be excluded 
