MARINE BIOLOGICAL STATION AT PORT ERIN. 41 



minute living things infesting and colouring the sand-grains of 

 our sea-beaches — I add here a further letter sent to " Nature " 

 (see September 4th, 1913, p. 5) during our summer cruise in the 

 Hebrides. 



* — v 5t~ / 



m 



/ k 



Fig. 6. Various forms of Amphidinium found on November 18th, 1912 ; 

 a to g encysted and immature stages ; h and i the larger (possibly new 

 to science) and the shorter (typical A . operculatum) forms for comparison ; 

 j side view of i; k, I and n stages of short form ; m a fission stage. 



" A varied and interesting field of investigation awaits 

 the microscopist who will make a detailed examination of the 

 minute fauna and flora of apparently barren sands on the 

 sea-shore. To-day, on landing at the island of Oronsay at 

 low tide, the otherwise pure white sand was seen to be coloured 

 pink in one area, for an extent of several yards, green a little 

 further up the beach, and golden-brown in small patches here 

 and there. On examining samples with the microscope the 

 brown colour was found to be due to living diatoms (not 

 Dinoflagellates in this case), naviculoid forms like Caloneis ; 

 the pink is formed of amorphous masses of fine granules in a 

 jelly loosely adhering to the sand-grains, and may perhaps 

 prove to be bacteria in a zoogloea state, while the green is 

 caused by patches of a very simple alga (? a Coccophycid) made 

 up of groups of rounded green cells in a single layer on the 

 sand-grains. I have kept samples of all the organisms and will 



