VARIATION IN THE DESMIDER. 977 
to state that the figure by which a person has illustrated one 
of his own species is not aceurate, yet it is undoubtedly 
true that many of these figures can be seen at a glance to be 
erroneous, not merely in detail, but also in their proportions, such 
proportions as are represented being incompatible with the 
symmetry of the plant. 
A careful serutiny of any species of Desmid suffices to demon- 
strate in its external morphological characters the presence of 
an inherent Symmetry and Repetition of Parts, and if, by careful 
study, the nature of this Symmetry were thoroughly understood 
in each species described, many unfortunate misconceptions and 
much useless synonymy would be avoided. 
1. PENTIUM sPrROsTRIOLATUM, Barker, in Quart. Journ. Mier. 
Sc., New Ser., vol. ix.p. 194.—This interesting speeies, whieh is 
widely distributed through Europe and N. Ameriea, and is also 
recorded from India, Burmah, and Siberia, was described by 
Barker (7. c.) in 1869 from specimens obtained in Ireland, and 
was first figured by Turner in 1885 (“Some New and Rare 
Desm.," Journ. Roy. Mier. Soe. ser. IT. vol. v. t. 16, f. 26) from 
specimens obtained from Minnesota, U.S.A. In 1875 a plant 
was described by Jacobsen as Closterium spiraliferum (“ Desm. 
Danm.,” Botanisk Tidsskrift, Kjóbenhavn, p. 177, t. 7. f. 8) 
and in 1883 Schaarschmidt described Penium Haynaldii (* Magyr. 
Desm.,” Magyar. Tudom. Akad. math. s. Természettud. Közle- 
mények, vol. xviii. p. 277, t. 1. f. 20). These two plants are un- 
doubtedly forms of this species. More recently, in 1893, Turner 
has given diagnoses and figures of three forms which he distiu- 
guishes as P. spirostriolatum, Barker, P. Royanum, W. B. Turn., 
aud P. scandinavicum, W. B. Turn. (cfr. Kongl. Sv. Vet.-Akad. 
Handl. Bd. xxv. no. 5, pp. 165-6. t. 23, ff. 3-7). These are un- 
doubtedly inere forms of one species ( P. spirostriolatum, Barker), 
and are not very accurately described or figured. Figures of this 
species were also given by West in Journ. Roy. Micr. Soc. 1890, 
t. 6. f. 24, but these are not very accurate. 
The following observations were made from a large series of 
students of the Rotifera would exercise more eare and discretion, and avoid 
giving new names on the slightest pretext, when it is well known that in many 
cases the original figures and descriptions are not perfect or complete, and that 
most specics are liable to considerable variation,” 
