OBSERVATIONS ON THE VOLVOCACEAE. 333 



There is yet another interesting behaviour on the part of these 

 organisms. Very early in the mornings the organisms are not so 

 noticeable, but a little later they swim actively all over the water. 

 Towards the middle of the day they recede below again, and towards 

 the evening they float up and form a sort of green mucilaginous 

 film on the surface. In this condition they are generally more 

 quiescent and often are dividing and forming daughter cells or 



colonies. 



Beach Pools 



Sand is removed from the Madras Beach for building purposes 

 and fairly deep hollows are formed in the sands very near 

 the shore. During the monsoon seasons a large quantity of rain- 

 water flows down from the Marina Road (which runs parallel 

 to the seashore and is at a higher level than the sandy beach), 

 and fills up these depressions in the sand. Again during the rainy 

 weather the waves are rougher and some sea water also flows over 

 the sandy shore into these pools. These pools, sometime after their 

 formation, both during the summer monsoon and winter monsoon 

 seasons, are soon peopled by large numbers of some member or 

 members of the Volvocaceae. The most interesting feature of these 

 pools is that the wet sand all round the edge of the pool to a 

 distance of a foot or two is quite green. On lightly scraping the 

 surface with a knife I found that the sand was green only near the 

 surface. Microscopical examination of the wet sand revealed a 

 large number of Chlamydomonas and other members of the Volvo- 

 caceae swimming actively in the thin film of water surrounding the 

 sand particles. Some of this green sand was collected by scraping 

 the surface lightly and shaken with some water. The water became 

 quite green leaving the sand in its normal colour. A drop of this 

 green water examined under the microscope showed the organisms 

 actively swimming about. I found this same preference for the 

 wet banks in other similar situations also. The organisms prefer 

 this situation probably because of better conditions of aeration. In 

 another instance I found that a depression in the beach sands was 

 merely wet at the bottom without any water in it. The surface of 

 this depression was covered by a very thin layer of dry sand which 

 was blown over by the wind. On removing this dry sand lightly 

 with a knife I found the lower layer of sand wet and greenish. I 

 also found that the greenness was confined only to a thin layer at 

 the top and lower down the green colour was absent. I shook some 

 of this green sand with water and found that its greenness was 

 due to a large number of Chlamydomonadine cells which had lost 

 their cilia and were quiescent. 



2563—43 



