SEA-FISHERIES LABORATORY. 257 



It will be seen, moreover, that each of the three years, 

 and each of the three vertical columns, is represented by 

 a substantial number of gatherings, and that these 

 numbers are fairly equal, lying as all six do between 526 

 and 756. 



Of the total number (1,946) of samples, a small pro- 

 portion (73) were taken with larger nets — the shear, the 

 Yngel and the large Nansen — which cannot be regarded 

 as comparable with the rest. The shear appears to catch 

 about 15 times as much as an ordinary small tow-net, and 

 the large Xansen (100 cm. in diameter of mouth) about 

 10 times as much. The Yngel has at least the same 

 catching power as the shear net. Of the remainder, 511 

 are hauls taken with vertical closing nets (Hensen and 

 Nansen), not very different in size and catching power 

 from the ordinary tow-nets of 14^ inches diameter of ring, 

 with which the other 1,362 samples were obtained. Of 

 course individual nets differed somewhat in their catches 

 according to the shape and make, but when seven of them 

 (" Hensen," "Hansen," "Weight," "Otter," "Coarse," 

 " New," and " Old ") were used simultaneously day after 

 day, we believe a useful roughly approximate idea of the 

 proportional variations in the plankton can be obtained by 

 averaging the hauls so as to get a single figure per net for 

 each locality (see below, pp. 345-349). 



Outline of the Year's Work. 



Throughout the year, from January 1st, 1909, to 

 December 29th, Mr. Chadwick took " official " gatherings 

 across Port Erin Bay, generally twice a week, and some- 

 times more frequently. The S.Y. " Ladybird " (fig 1) was 

 fitted out for the season towards the end of March, and 

 her first plankton trip was on March 27th. From that 



