ARTIFICIAL CULTURE OF MARINE PLANKTON ORGANISMS. 411 



Skeletonema was not so good, and no Streptotheca was 

 found. 



On October 2nd (37 days) Biddulpliia was numerous and 

 healthy, Coscino discus was healthy but not so numerous, 

 Skeletonema was poor, and Chfetoceras was not seen. 

 Flagellates (Chilomonas) bad become very numerous. 



On October 31 st (66 days) all the diatoms were in very 

 poor condition, Coscinodiscus being slightly better than 

 the others. The flagellates (Chilomonas) Avere extremely 

 thick, giving the water a deep red colour. 



Subsequently a small green alga (Pleurococcus 

 mucosus) appeared, having probably been derived from the 

 Coscinodiscus culture. This increased very greatly in 

 quantity, whilst the flagellates become inconspicuous. 



On July 28th, 1909 (1 year 11 months) some Coscino- 

 discus, which were still in a healthy condition, were seen in a 

 sample examined from the flask. A great quantity of 

 Pleurococcus, in a healthy condition, was also present, but 

 no other oganisms were noted. On tins date a subculture 

 was made from the flask in normal outside Miquel. The 

 subculture gave a considerable growth of Skeletonema, 

 the cells being, however, of a very abnormal character, and a 

 good many normal and healthy Coscinodiscus were found 

 in each sample examined. The whole culture was crowded with 

 Chilomonas in a very active state, which gave the whole 

 contents of the flask a deep red-brown colour. Up to August 

 24th the green alga (Pl.eurococcus) had not become suffi- 

 ciently abundant to be detected by the naked-eye appearance 

 of the flask, though it could be seen in samples examined with 

 the microscope. 



In another experiment a flask of Miquel sea-water was 

 inoculated (May 4th, 1908) from two cultures, one containing 

 the green alga (Pleurococcus mucosus) and the other 

 Thalassiosira decipiens. At first both did well, and on 

 May 20th (16 days) there was a very good crop both of the 

 diatom and the alga. Gradually, however, the alga became 

 predominant^ and on October 14th (163 days) only quite empty 



