A Study of the Phy to- Plankton of the Atlantic. 269 



" A Study of the Phyto-Plankton of the Atlantic." By GEORGE 

 MURRAY, F.B.S., Keeper of Botany, British Museum, and 

 V. H. BLACKMAN, B.A., F.L.S., Hutchinson Student, St. 

 John's College, Cambridge, and Assistant, Department of 

 Botany, British Museum. Keceived March 28, Read May 

 12, 1898. 



(Abstract.) 



The authors record their observations on a year's work in collect- 

 ing phyto-plankton along a track from the Channel to Panama 

 carried ont by Captains Milner and Budge, and also during one 

 voyage to Brazil by Captain Tindall. They also give the results of 

 their own observations on living material at sea. The material was 

 obtained by the pumping method. 



One of the objects of their work was to determine, if possible, the 

 nature of the Coccospheres and Bhabdospheres. They describe the 

 minute structure of the calcareous plates or coccoliths and rhabdo- 

 liths, and record the existence in the Coccospheres of a single central 

 green chromatophore, separating into two on the division of the cell. 

 They regard Coccosphaeraceaa as a group of Unicellular Algee, and 

 they define the group, the limits of the genera and species. The 

 Coccospheres and Bhabdospheres from the surface are compared with 

 those of the deep-sea deposits and their identity established. They are 

 also compared with geological coccoliths and rhabdoliths from various 

 beds, and many objects regarded by geologists as true coccoliths and 

 rhabdoliths are rejected. A large number of new Peridiniaceaa were 

 discovered and are formally described and figured. No specific 

 diagnoses of marine Peridiniaceas have previously been published, 

 authors of species having depended on figures, and, at most, a few 

 words of description. It is hoped that the present systematic treat- 

 ment of the subject will conduce to greater order in the group. 

 The authors record the occurrence of all the forms in seven tabular 

 statements, one for each collecting voyage. 



Observations of the diatoms and Cyanophycese were also made, and 

 are briefly treated. 



A study was also made of the species of Pyrocystis, of which they 

 describe a new one. The facts they record tend, in their opinion, to 

 confirm the view originally expressed of it by Dr. John Murray, its 

 describer, that it is a unicellular alga, doubts having been entertained 

 of the accuracy ol this opinion by several biologists. 



YOL. LXIII. x 



