In the Laboratory 



The collections recoived the following treatment in the 

 laboratory s 



(1) All fish eggs and larvae were removed from samples taken 

 on Smith cruises 4 and So These amounted to a negligible 

 fraction of the sample and were omitted from the volume 

 measurements. For the other cruises the fish eggs and 

 larvae were not removed from the collections o 



(2) All organisms whose longest dimension we.s greater than 5 

 cmo were removed from tl-ie sample. The kind of organism 

 removed and its displacement vDl'jsioe were recordedo As 

 such organisms occurred infrequent ly^ they are emitted 

 from this analysis o 



(3) All organisms whose longest dimension was between 2 and 

 5 cm. were next removed from the sample i, identified as 

 nearlj'' as possible ^ and their displacement volume was 

 m.easurede 



(4) The remainder of the sample, those organisms measuring 

 less than 2 cm^ in their longest dimension and constitut- 

 ing the bulk of the sample, was examined under a binocu- 

 lar dissecting microscope and its general composition 

 was noted. The displacement volume of this fraction was 

 then determined after any artifacts, such as refuse, from 

 the ship, had been removed o Tliis portion of the sample 

 was not further subdivided » 



In measuring the displacement volume, the plankton was poured 

 into a draining sock of 56XXX grit gauze to filter off the preserving 

 liquids The drained plankton was then placed in a graduated cylinder of 

 approximate size (usually of 50 or 100 mlo capacity) o By means of a 

 bxirette a known volume of water was added to the drained plankton. The 

 difference between the volume of the plankton plus the added liquid and 

 the volume of liquid alone was recorded as the displacement or net wet 

 volume of that portion of the plankton sampleo 



For an estimate of the amount of zooplankton in each sample 

 that was potentially fish food of significant nutritional value, the dis- 

 placement volumes of the following were useds 



(l) The entire remaining fraction of the sample after the 

 larger organisms, 2 cmo or greater in their longest 

 dimensions had been removed o 



Ordinarily this portion of the san^le was composed 

 primarily of crustaceans and chaetognaths with a small 

 percentage by number and volume of "watery" organisms of 

 low food value, such as jellyfish and salpso As stated 



