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Notes on the Plankton observed at Plymouth during 

 June, July, August and September, 1892. 



By 

 Edward J. Blcs, B.j§»c., 



Hon. Research Fellow in the Owens College. 



The absence of systematic records showing the variations of the 

 floating fauna and flora, or plankton, of the Plymouth waters is much 

 to be regretted. My observations on the amount of animal and 

 plant life suspended in the sea from the surface to the bottom 

 would show that in comparison with similar observations made 

 elsewhere, the quantity of plankton in this locality was during the 

 past summer surprisingly small. The absence of data upon which 

 comparisons could be based between the state of the water in this 

 season and that obtaining in former years is all the more to be 

 deplored because the present season has in many respects been a 

 remarkable one. In the first place, the Plymouth mackerel fishery 

 has so far been a complete failure ; it has further been found that 

 dog-fishes (both Scylliuvi and Acanthias) were not obtainable during 

 June and July ; and lastly, Aurelia aurita, which in summer isiisually 

 common, was extremely scarce in the Sound and tidal waters of 

 Plymouth. If my surmise that the amount of plankton was for the 

 locality exceptionally small proves correct, then these three salient 

 instances of scarcity of animals which are directly or indirectly 

 dependent on the plankton for their food will suffice to show the 

 importance of a series of more or less continuous observations on 

 the physical and biological condition of the inshore and Channel 

 waters. Were accurate information on these points available, it 

 would in all probability enable us to explain, and we might even in 

 time be able to foresee, the occurrence of so important an event as 

 the exceptionally sporadic appearance of the mackerel in 1892. 



The quantitative and faunistic observations I have made with 

 the aid of a Royal Society grant are made with this object in view, 

 but it will be some time before the results are ready for publi- 

 cation, and it may now be of interest to record some extracts from 

 my diary. 



June 17th. — Hormiphora plumosa, the Ctenophore common at 



