The Genus Microcystis in Ceylon 67 
forms, which are not so obviously distinguishable from M. flos-aquce, 
the colonial mucilage does neither stain with Safranin nor Methyl 
Violet 5 B, whereas in the latter species the mucilage is irregular 
and stains deeply with these colouring reagents. The cells in both 
species stain deeply with Methyl Violet, this stain showing them to 
be surrounded by an individual membrane of moderate thickness. 
The presence of an individual membrane around the cells has been 
used by Lemmermann to characterise the genus Coelosphceriopsis. 
In the latter these cell-envelopes are apparently visible without 
staining. The presence of individual membranes in Ccelosphcerium 
dubium, although less obvious, shows there is no fundamental 
distinction between the two genera. In Microcystis we meet with 
all stages of differentiation of the cell-envelope even in one and the 
same colony (see figure of M. viridis in (i)) and in the Chroococcaceae 
in general the presence or absence of such an envelope has been 
shown to be of little direct systematic importance (l). 
C. dubium was found in the following localities: tank at Dam- 
bulla, Sept. 9th; tank at Haberane, Oct. 10th; Lake at Candy, 
Sept. 24th; tank Tissawewa near Anuradhapoora, Oct. 3rd. 
SUMMARY AND CONCLUSIONS 
1. The genus Microcystis is represented in the freshwater plankton 
of Ceylon by at least eight species, two of which are described as new. 
2. The species are connected by numerous transitional forms, the 
nature of which is described. 
3. The distinctions between the species of Microcystis are of the 
same kind as between other cogeneric species of Cyanophycece. 
4. The present distinction between Aphanocapsa and Microcystis , 
in view of such a species of M. protocystis n. sp. is seen to be an artificial 
one. The former genus consists of forms of various affinities. 
5. Ccelosphcerium dubium Grun. is related to the species of Micro¬ 
cystis possessing pseudo vacuoles, although genetically distinct from 
them. Ccelosphceriopsis Lemm. is not distinguished by a valid generic 
character. 
In conclusion my warmest thanks are due to Prof. F. E. Fritsch 
for providing the material for the above investigation. 
DIAGNOSES OF NEW SPECIES 
Microcystis protocystis n. sp. 
Strato libere natante, irregulario, saepe diffuso, tegumento strati 
non plane delimito, interdum vel nil vel evanescente. Cellulis numero- 
5—2 
