H>'NEAN' SOCIETY OF LONDON^. 20 



respectively. On most occasions of course thej were very similar 

 and on some absolutely 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 

 freqiiently, and in fact usually, obtained a larger gatherino- and 

 showed a greater variety of organisms than either the bottom 

 (vertical) or the surface nets. 



On some occasions, at the "along-shore" stations (e. g., 2 miles 

 off Bradda Head) hauls were taken with a new " shear-net " made 

 on the principle of the Heligoland " Scherbrutnetz " {Conseil Inter- 

 national — llapports et Proces-verh., vol. ii. p. 62, 1904). This was 

 used as a mid-water net — being lowered to a depth of 5 to 10 

 fathoms, where, through the action of the shearing plate, placed 

 like a vertical otter-board, it remained even when the ship went 

 ahead at a moderate speed, and so formed a most efficient instru- 

 ment of capture in waters where the ordinary net cannot be towed. 

 The mouth measured 9 feet in circumference, the net was over 

 10 feet in length, and being formed of rather coarse mesh caught 

 large quantities of the larger organisms of the plankton such as 

 Sagitta, Medusae, Ctenophora, Zoeas, the larger Copepoda and 

 some young fishes. 



As a vertical closing net I greatly prefer the Nansen to the 

 Petersen-Henseu. It is lighter and less complicated (a matter of 

 some importance in a rough sea), more easily manipulated, less 

 liable to failure in action, costs less and seems to catch more for its 

 size of opening. 



The localities to be sampled, all within a ten-mile radius of 

 Port Erin, were — the two "off-shore" stations, No. I., 5 miles, and 

 No. II., 10 miles, from Bradda Head respectively, and three "alono-- 

 shore " stations, No. III. towards Niarbyl, No. IV. towards the 

 Calf Island, and No. V. off Spanish Head. The nets to be com- 

 pared were: — two vertical deep-water, the Nansen and the Petersen- 

 Henseu, and three horizontal, one weighted and the other two 

 surface. In addition a shear-net gathering was taken on occasions 

 from intermediate waters. Each haul was a 15 minutes one. 



I shall append (pp. 32-33), in tabular form, my first statement of 

 results, which may require to be modified in detail or supplemented 

 later on, but which may be taken as substantially correct. Whether 

 one looks at the hauls Avith the same net at the one locality on 

 different days, or at neighbouring localities on the same day, the 

 want of uniformity both in quantity and in quality is striking. 

 The range for all nets is from 0-5 c.c. to 164 c.c, and it is the same 

 for the Nansen ; for the Petersen-Hensen it is from O'o to 04-5 c.c, 

 for the weighted open net from 5*5 to 41 c.c, for the surface 

 nets from 1 c.c to 42'5 c.c, and for the shear-net from 11 to 

 78-5 c.c. 



One or two broad features of the collection are obvious. la the 

 earlier part of the time, up to about the middle of April, Diatoms 



