VARIATION IN THE DESMIDIEX. 403 
having given a conclusive argument in favour of the view that 
the Desmidiex constitute a degenerate family of Conjugates. 
I append a full aecount of all that is known of the variation 
in the conjugation of these plants :— 
1. Closterium Pritchardianum, Arch. Zygospore formed by 
the conjugation of three cells: West & G. S. West in Journ. 
Roy. Mier. Soc. 1897, p. 480, t. 6. f. 5. 
9. Cosmarium nitidulum, De Not. Zygospore formed by the 
conjugation of four cells; erroneously recorded as a new species 
— C. rectosporum—by W. B. Turner in Kongl. Sv. Vet.-Akad. 
Handl. Bd. xxv. no. 5 (1893), p. 69, t. 10. f. 16 e. 
3. Cosmarium Regnesii, Reinsch. Variability in form of 
zygospore: West & G. S. West in Journ. Roy. Mier. Soc. 1896, 
p. 155, t. 3. ff. 30-31. 
4. Staurastrum teliferum, Ralfs. Zygospore formed by con- 
jugation of three cells: West in Journ. Linn. Soc., Bot. vol. xxix. 
(1892) p. 175, t. 24. f. 5. 
5. Hyalotheca dissiliens, Bréb. Abnormal conjugation men- 
tioned by Joshua in Journ. Bot. vol. xx. 1882, p. 301; “ cell. 
copul. monstr.” described and figured by Boldt in Bihang till 
K. Sv. Vet.-Akad. Handl. Bd. xiii. Afd. iii. no. 5, 1888, p. 43, t. 2. 
f. 53; cfr. also West & G. S. West in Ann. Bot. vol. xii. 1895, 
p. 53, t. 4. f. 37. 
V.—Some Interrelationships of the Desmidiee deduced 
from a study of their Variation. 
The foregoing account of variations observed in a natural 
state enables us to adduce evidence which offers some clue to 
the relationships that exist between many different forms, and 
it realizes in part that which should be one of the main objects 
of classification, namely, how species may be brought into rela- 
tionship one with another. The importance of this study cannot 
be overestimated, as it is the surest means of arriving at the 
most approximate limitations of what we call ‘ species,’ and only 
after the attainment of a competent knowledge of the variability 
in the group can we form a conception of the evolution of 
Desmid-forms. 
The question of the specific distinctness of many of these 
plants has been raised many times and by many people, and 
although it is one which will take a very long time to answer, 
yet astudy of their variation will go far towards its solution. 
