334 THE JOUENAL OF INDIAN BOTANY.
This invasion by the free swimming Chlamydomonas of a wet
sub-aerial region, in the first place, and, in the second place, its losing
its cilia under a comparatively drier condition, suggests a probable
method by which some of the sub-aerial unicellular Green Algae might
have evolved from some free swimming Chlamydomonadine type.
Genera collected
The following genera have been collected by me at Madras : — Chlamydomonas, Carteria ; Gonium, Pandorina, Eudorina, Pleodorina and Volvox. The most common ones were Chlamydomonas and Car- teria among the unicellular forms, and Pandorina and next Eudorina among the coenobial forms. Gonium was a rarer form. Pleodorina was still rarer. But the rarest was Volvox.
These forms I must however point out were always associated with a sprinkling, large or small, of other plankton forms of Algae, and Flagllate (such as Euglena, etc.).
One feature which was particularly noticeable in the summer rain-water pools was the complete absence of Spirogyra and the other filamentous Green Algae, and the extreme scarcity of the Blue Green Algae.
Enemies of the Volvocaceae
The bottom of the pools very often showed large numbers of amoebae ; and these injested a large number of the unicelluler algae during the times when the latter settled down at the bottom. I came across many amoebae, with Chlamydomonas in their bodies and I saw some actually in the act of in jesting them.
In another pool I found Pandorina and Eudorina swimming with one or two, sometimes even four, or five, small round colourless Protozoons attached to their mucilaginous envelope. On further exa- mination I found that these Protozoons gradually made their way in- side and swallowed some of the cells of the colony. Later on they escaped from the colony leaving a big rent in the mucilaginous enve- lope. Many specimens of Pandorina and Eudorina were found by me with a big rent in their body and a few of their cells missing.
Another enemy which plays havoc with these forms is a kind of Eotifer. This was found in very large numbers in a tub containing Pleodorina and Eudorina devouring them in large numbers.
I came across a Chironomus larva ("Blood-worm"), devouring large quantities of Pandorina. This larva has the habit of constructing out of the materials of its environment such as silt, etc., a kind of case for itself by fastening with the help of a silk-like secretion of its sali- vary glands. I kept some quantity of live Pandorina in a dish. The next morning I found a large number of green cases attached to the
