62 
W. B. Crow 
Observations on the Ceylon material show similar transitions. 
Moreover, it is clear that reproduction of the colonies largely takes 
place by vegetative breaking. Hence a clathrate colony may break 
up into non-clathrate masses, which in their turn may undergo the 
process of reticulation. The forms recorded here as M. ceruginosa are 
such as show little or no reticulation. 
Most of our colonies had an indistinct outline. But those from 
Colombo Lake often had a very definite marginal region when seen 
in optical section. This was especially marked in those colonies that 
were breaking up into numerous daughter colonies as shown in Fig. b. 
Sometimes the partial colonies were mere nests of less than a dozen 
cells, surrounded by a wide clear sheath. Formation of daughter 
colonies often appears localised so that the former may appear as 
buds upon the latter. Possibly these appearances represent successive 
stages in the breaking up of the colony. It is only the fact that such 
small colonies are found in actual process of formation that proves 
these forms to be connected with typical colonies of M. flos-aquce, 
for the latter are much larger and have a far more indefinite colonial 
mucilage sheath. 
Other variant colonies of M. flos-aquce approach M. scripta and 
M. ochracea in a tendency to produce outgrowths. But the typical 
lobing of the definite type figured for these latter species was not 
met with in the collections examined. We have preferred to retain 
M. flos-aquce as a distinct species since the forms as described above 
often occur in large quantity and cannot all be explained as develop¬ 
mental phases of other species of Microcystis. 
Loc. Lake at Candy, Sept. 24th; lake at Colombo, — ; four 
small tanks near entrance to Botanical Gardens, Anuradhapoora, 
Oct. 2nd; tank Mineri, Oct. 12th (water-bloom); tank Tissawewa, 
near Anuradhapoora, Oct. 3rd; small rock pool, in wet season of 
the year certainly connected with tank Punchi-kekirawa close by. 
Sept. 28th. 
MICROCYSTIS PROTOCYSTIS n.sp. 1 
Fig. d 
Colonies irregular, often diffuse, with colony-sheath not clearly 
delimited, sometimes disappearing. Cells very numerous, varying in 
mode of aggregation from closely crowded to generally dissociated, 
spherical, 3*5-6*5 ^ diam., with pseudovacuoles. 
1 A Latin diagnosis of this and other new species is given as an appendix. 
