57 



OCCURRENCE OF AMPIIIDINIUM 

 OPERCULATUM AT CULLERCOATS. 



By OLGA M. JORGENSEN. 



Previous to the autumn of 1917 this form was recorded from 

 Cullercoats Bay on only two occasions. The first time it was 

 noted was on May 25th, 1913, when Mr. Storrow "^ observed small 

 patches of sand coloured by Amphidinium operculatum at the 

 north side of the bay. It remained for several days. It was not 

 noted again until the next year when Mr. T. Whitehead t gave a 

 short account of his observations. A. operculatum occurred on 

 the foreshore in much larger numbers than last year in two 

 patches N.E. and E. of the Laboratory, and a few feet below 

 high water mark. These patches proved to be an almost pure 

 culture of the species, and consisted chiefly of encysted forms. 

 These patches persisted until the end of vSeptember. (When 

 they were first observed is not stated.) 



Although I had noted the occurrence of Amphidinium in the 

 plankton samples which T examined from time to time, my atten- 

 tion was not particularly attracted to it until September, 1917, 

 when a sample was brought into the Laboratory from the north 

 end of the bay, where it occurred in patches on the wet sand. 



From this time the characteristic brown patches were looked 

 for at frequent intervals, but not until November 29th did they 

 appear again, when wet stretches of sand below the Laboratory 

 were covered with faint brown markings. On the following day 

 a tour of the foreshore was made from the north side of the 

 Laboratory to the south end of the bay, when immense quantities 

 of Amjjhidinium were found to be present throughout the tidal 

 zone, wherever water remained on the surface of the sand. A 

 number of sandy pools among the rocks at the high tide mark 

 showed still larger quantities, lying in deep brown patches on the 

 sand. There did not appear to be any in the water. The examina- 

 tion of a sample showed that these forms were very active. 



* " Report of the Dove Marine Laboratory. Cullercoats," 1913. 

 t " Report of the Dove Marine Laboratory, Cullercoats," 1914. 



