56 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



by the June Navicula, I found to my surprise that the 

 brown patches on the sand were once more present, and 

 now showed dense swarms of Amphidinium, but no 

 Diatoms. This condition remained for a few days, and 

 then disappeared, and on the 16th the Naviculoid 

 Diatoms were back again in force and remained abundant 

 during the 17th and 18th of September. On the last two 

 dates some small and rather greener patches were found 

 which on examination proved to consist of a bright green 

 Euglenoid Infusorian. The Amphidinia made theii 

 appearance next on October 2nd, and remained more or 

 less in evidence during the month. They were in. great 

 abundance on the 12th and 13th, again on the 19th, and 

 finally, on the 25th and 26th. No Amphidinia were 

 found between October 28th and November 1st, 

 but on November 2nd some small patches again made 

 their appearance in the usual positions on the beach and 

 then died away. 



The following may be given as a brief tabular 

 statement of these remarkable alternations of the animal 

 (Amphidinium) and the plant (Diatoms) on the beach at 

 Port Erin during these seven months in 1911. 



April 7 to May 1 ... Amphidinium, and a few Diatoms (Navicula) 



June 3 to July 22 ... Diatoms (some Navicula, others Pleurosigma) 



Sept. 9 and 10 ... Amphidinium in abundance, Diatoms absent 



Sept. 16 to 18 ... Diatoms (naviculoid) 



Oct. 2 to 26 ... ... Amphidinium in abundance, Diatoms absent 



Oct. 28 to Nov. 1 ... No Amphidinium present 



November 2 ... ... Amphidinium (3 small patches) 



Since this date neither organism has been found, 

 and no brown patches have been seen on the sand. 



Presented in this form the evident alternation 

 between these two kinds of organism is very striking, 

 and, although it may be impossible as yet to give any 

 full explanation, still the facts seem to point to the 

 probability that the cause of the phenomenon is a 

 physiological one and that the explanation may consist in 

 showing that each organism in turn in its metabolism 



