MARINE BIOLOGICAL STATION AT PORT ERIN 63 



which, it gradually rose as the ship went slowly ahead ; 

 while the other two (B and C), unweighted, remained 

 continuously at or just under the surface and worked side 

 by side like a pair of sharks or porpoises .swimming in 

 our wake. These two last nets ought, if there is any 

 uniformity whatever in the plankton even in the most 

 limited areas, to give similar results, and of course they 

 did so in most cases. My purpose in taking the two 

 similar surface nettings side by side was to show this, 

 and also to test the reliability of the sample ; for I would 

 only consider it a trustworthy sample when these two 

 nets agreed in their evidence. Where, under the circum- 

 stances stated above, the gatherings differed notably, 

 there must have been some accident in the working of the 

 nets or some abnormality in the distribution of the 

 plankton, such as, no doubt, will sometimes be en- 

 countered when traversing the edge of a swarm of gre- 

 garious organisms ; and it is important to get some 

 evidence as to how frequently such accidents or abnor- 

 malities may be met with. For example, on April 2nd, 

 at Station III., I find that the two surface-nets used 

 together gave 17 c.c. and 42'5 c.c. of material respec- 

 tively; on April 9th, at Station I., 2'5 and 8 c.c. 

 respectively; and on April 24th, at Station II., they gave 

 T c.c. and 15 c.c. respectively. On most occasions, of 

 course, they were very similar and on some almost 

 identical in their catch. 



The net A (which may be called the weight-net) is of 

 use as having traversed a wider range, to 10 fathoms, 

 so as to sample all the water above the zone traversed by 

 the vertical nets, and it frequently, and in fact usually, 

 obtained a larger gathering and showed a greater variety 

 of organisms than either the deeper, closing (vertical), or 

 the open surface nets. 

 F 



