SEA-FISHERIES LABORATORY. 273 



that the lowest observation, that of June 22nd, occurred 

 after rain. Since, however, the water from which the 

 samples were taken had moved from some other district, 

 it is quite obvious that variations might be determined by 

 weather conditions elsewhere. There does not appear to 

 have been any particular change in either temperature or 

 salinity conditions accompanying the sudden disappear- 

 ance of the Diatoms between May 21st and 28th. The 

 differences between surface and bottom salinity on the 

 three occasions when samples were taken are 000, 0*05 

 and 0*11 respectively. 



PLANKTONIC RESULTS. 



Under this heading we shall consider the plankton of 

 Port Erin Bay and that of the open sea outside, the 

 distribution of the more important groups, such as 

 Diatoms and Copepoda, and of selected genera of these 

 and other groups, the proportions of Oceanic and Neritic 

 species in our fauna, the relation of the plankton to 

 sunlight and its distribution in depth, the plankton as the 

 food-supply of the sea, and finally shall discuss the 

 results obtained by different types of net. 



Plankton of Port Erin Bay. 

 Our aim has been to obtain tow-net gatherings taken 

 across Port Erin Bay on at least two days in each week 

 throughout the year — both fine (No. 20 silk) and coarse 

 (No. 9) nets being used on each occasion, thus giving four 

 gatherings in each week. Mr. Chadwick (by whom most 

 of these " Bay " gatherings were taken) has carried out 

 our intentions so well that we have in all 231 samples, 

 and these represent every week in the year except the 

 second week in January, a time of continuously bad 



