sea-fisheries laboratory. 229 



Plankton Observations. 



The plankton hauls, taken as frequently as possible 

 simultaneously with the temperature and salinity obser- 

 vations, were in all cases made with the same nets and by 

 the same method so that the various gatherings might be 

 as nearly comparable as possible. All the vertical hauls 

 were made with the smaller Nansen closing net, of No. 

 20 silk, and having a mouth 35 cm. in diameter. Surface 

 hauls were sometimes taken at the same time, with 

 ordinary open surface tow-nets made of the same silk 

 (No. 20) as the Nansen net and of approximately the 

 same size of mouth. The Lucas sounding machine, fitted 

 with 200 fathoms of pianoforte wire, was used in all cases 

 in taking the vertical hauls — 'down to a depth of 135 

 fathoms. 



The list given below at page 230 shows the complete 

 series of these plankton gatherings, which will be found 

 to represent most of the localities dealt with in our paper 

 in last year's Report, and we have, moreover, extended 

 this year the observations considerably further to the 

 north — from the Island of Skye to the Shetland Isles. 

 We do not propose in this year's Report to make a 

 detailed analysis of these hauls, as we hope to be able to 

 repeat a number of the observations in the coming 

 season ; but in comparing even the brief descriptions 

 given in cur list with the characteristics of the plankton 

 at the same localities in last year's Report, we notice 

 certain differences which we desire to point out. For that 

 purpose we shall group this year's 70 gatherings into 

 seven areas comparable as far as possible with those of 

 last year's Report, and shall indicate briefly the nature 

 of the plankton in each and note any differences that are 

 seen. 



