PLANKTON OBSERVED AT PLYMOUTH. 343 



fusion of this infusoriaiij which in the months of June and July was 

 present in such numbers that it discoloured large stretches of sea. 

 This year it has been almost entirely absent, and a few individuals 

 which I found at the end of September were the only signs of its 

 existence. There were no great displays of phosphorescence this 

 summer, either in the Sound or in the Channel, on the occasion of 

 my nocturnal excursions. 



Seiitemher SOth. — Two species of Copepods which, according to 

 Bourne (this Journal, vol. i, pp. 150 and 151) have only been taken 

 here from February to May, I found outside the Breakwater in 

 September. They are Euterpe gracilis and Corycaeus anglicus, the 

 former being fairly plentiful. During the whole summer Cetochilus 

 septentrionalis has been present, but never in large numbers, each 

 tow-netting generally containing a few. 



In the last days of September a marked increase in the number 

 of Dinoflagellates took place, and among them a form appeared 

 which seems to be intermediate between Dinophy sis and Ornithocercus, 

 but which I have not yet identified. 



I have collected a number of interesting Annelid and Mollusc larvae, 

 which I have not mentioned above, as I hope to report on them in 

 detail elsewhere. 



I have found that it is easy to rear Annelid and other larvae by 

 the following method : — The whole of a tow-netting in a large con- 

 fectionery jar full of pure sea-water may be placed up to its neck in 

 a tank through which water circulates. If the tow-netting is rich 

 in species but poor in individuals, a large number of larvae will live 

 and continue to develope. Such a tow-netting I obtained on 

 September 5th, and in seven to ten days later, after keeping the 

 bottle at a constant low temperature in the way described above, I 

 found on the sides of the bottle young Serpulids in tubes, a few 

 two- three- aud four-celled colonies of Membranipora and young 

 bivalve molluscs in the prodissoconch stage. I also found four 

 specimens of Protodrilus leuchartii, Hatschek, a most interesting 

 Archiannelid which has until now, I believe, not been recorded from 

 any other locality but the Mediterranean and Black Sea. 



