Table 2. --RcbuUb of four test hauls showing differences in the estimated depth 

 reached, employing three methods of determination 



triangles. However, it should be noted that in the waters traversed during this cruise there is 

 marked horizontal shearing associated with differential current flows which undoubtedly exert a 

 strong influence on the shape of the towing cable with its attached instruments. Under these con- 

 ditions the actual depth of sampling will vary considerably from the estimated depth, especially 

 when the latter has been derived from average relations. It is regretted that a continuous depth 

 recorder was not available at the time of the cruise. 



Treatment of Samples in Laboratory 



500 

 400 

 300 





^ 10 20 30 4050 100 200 400 1000 



ESTIMATED DEPTHS BY STRAIGHT-LINE METHOD(M) 



Figure 3. --Combined results of the four test hauls, 

 plotted on a logarithmic scale, showing the rela- 

 tionship between estimated depths based on straight - 

 wire and curved-wire calculations. The regression 

 coefficient (b) = 1. 1238. 



In the laboratory, displace- 

 ment volume measurements were made 

 on the 68 acceptable samples. First 

 the few organisms with longest dimen- 

 sion greater than 2 cm. were removed 

 from the sample, identified as precisely 

 as possible, and their displacement 

 volume measured. Then the volume of 

 the remainder and bulk of the sample, 

 i.e. those organisms with longest di- 

 mension less than 2 cm. , was deter- 

 mined. In measuring the displacement 

 volume, the plankton was poured into 

 a draining sock of 56XXX grit gauze to 

 filter off the preserving liquid. When 

 the sample stopped dripping it was 

 transferred to a graduated cylinder of 

 appropriate size (usually 5 or 10 ml. 

 capacity). By means of a burette 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 added 

 liquid was recorded as the displaceme"-t 

 or net wet volume of that portion of the 

 sample. 



