58 LINNEAN SOCIETY OF LONDON'. 



stations in u hicli Brachiomonus has been found : Sheerness in 

 Kent, .Stockholm in Sweden, and Constanta on the Black Sea — 

 in all cases in brackisii water. 



It must bo presumed, therefore, that in the present case the alga 

 was transported a distance of at least forty miles, either by wind 

 to be deposited e\entiially by rain, or possibly by the sea-birds 

 which visit Kegent's Park constantly. One must not forget, 

 however, that if the plant occurs at Sheerness, it may extend up 

 the estuary of the Thames, even though unrecorded. Although 

 the distance travelled in the latter case would not have been so 

 great, the mechanism of transport remains an unsolved problem. 



During the fortnight or more that the plant was kept under 

 observation, it appeared to be in perfectly healthy comlitioii, in 

 spite of the fresh-water habitat. 



The earliest account is that of K. Bohlin (1897), whose material 

 \\as obtained from brackisii water off tlie Swedish coast, the 

 salt content of the water being about one-third that of the open 

 sea. A second description is given by E. C. Teodoresco of 

 material obtained by him at Constanta on the Bhick Sea. There 

 the alga was found under similar conditions to those described by 

 Bohlin, viz. in rock pools containing brackish water. A description 

 in considerable detail is given by (t. S. West (1907) of material 

 obtained from brackish marshes at Sheerness. The alga was then 

 reported to be common there in February: whether this is still 

 the case I have not ascertained. 



Bohlin distinguished two species, B. suhmarina and B. r/racilis, 

 the former possessing a more spherical and massive bodj' and 

 shorter horns. West referred the Sheerness organism to B. sub- 

 iiiai'liia after some hesitation, since the specimens showed much 

 variability and were, on the whole, intermediate in form, none 

 having processes so short as figured by Bohlin for B. suhmarina, 

 nor the anterior ])art of the cell so flattened or the posterior horn 

 so long as figured for B. r/racilis. The London samples also 

 showed very great variability. If there are t«o species of 

 Brachiomonas, then I think it likely that both were present in 

 the samples examined by me. An alternative view is that one is 

 dealing with a single species which exhibits a great range of form. 



To summarise: — Brachiomonas, a genus hitherto recorded only 

 from three widely-separated stations in brackish water, is now 

 put on record for London growing in fresh water under conditions 

 which .suggest that it may have been deposited with rain or 

 brought by sea-birds. The individual plants showed great varia- 

 bility of form, ranging between the types figured by Bohlin as 

 B. suhmarina and B. gracilis. 



My thanks are due to Prof. F. E. Fritch for identifying the 

 material as B, suhmarina. 



References. 

 Bohlin, K. — Zur Morphologie und Biologie einzelliger Algen, 

 Ofversigt af Kongl. Yet.-Akad. Fcirhandl. 1897, No. 9, 

 Stockholm. 



