APPARATUS USED WITH PLANKTON NETS 189 



Others, it is almost equally efficient, a good deal easier to handle, and can if necessary 

 be closed on the Nansen principle. 



It is an excellent net, yielding large catches of macroplankton with a wide range in 

 size. It was used effectively at all depths. 



Other Plankton Apparatus 

 The Continuous Plankton Recorder, a new instrument for giving, as the name im- 

 plies, a continuous record of the plankton through which it has been towed, was tested 

 on many occasions and in all recorded just over 2400 miles of plankton. A preliminary 

 description has already appeared ;i the full description will be published later in a 

 report dealing with the results obtained by its use. Small plankton indicators^ were 

 occasionally used to indicate the presence or absence of diatoms or young Euphausians. 



Buckets for Vertical Nets. In order to save time on routine stations when a 

 number of vertical hauls are taken — and time in intensive plankton work is a vital 

 factor — special buckets were designed. These are shown in Figs. 13 and 14. They 

 are m.ade of phosphor bronze and consist of two main parts: the holder a, a cylinder 

 attached to the canvas end of the net by the band d, and the easily detachable 

 bucket b, which is screwed tightly up to the holder a by the loose collar c. The 

 collar is well milled, so that it can be tightly screwed up and quickly undone, and 

 held to the holder a by a flange. The inside of the holder which fits into the canvas 

 cod-end of the net is gently bevelled at the top so that no organisms can stick round 

 the edge. The collar d grips the canvas where it joins the silk netting immediately 

 round the outside of this edge ; a piece of tape or rubber inside this band improves the 

 grip. On the outside of the holder are three eyes g, to which are seized the supporting 

 wires to the weight below. The bucket b bears a strong screw thread round its upper 

 margin for engagement with the collar c. Below this is a series of windows covered 

 with phosphor-bronze gauze: 140 meshes to the inch in the N 70 and 200 meshes to 

 the inch in the N 50. Thus when the net leaves the water and is washed down, the 

 plankton sample is reduced to a reasonable size in that part of the bucket below the 

 windows. It is then unscrewed, replaced by another similar bucket, and is closed by 

 the screw-on lid /, so that it may be put down without fear of upsetting, and the work 

 carried on. Each lid bears on the top an oblong strip of ivorine, upon which the 

 depth from which the haul was taken may be written. Opposite the gauze windows the 

 top of the jar is hollowed out on the inside to form a lip for pouring out the sample. 

 The windows of the larger jar are so shaped that they are the maximum size that will 

 allow the sample to be poured out from the opposite side without fouling them : those 

 of the smaller jar are made small and circular on account of the fragile nature of the 

 very fine-meshed gauze. After the sample has been poured out a little water is washed 

 through the windows from the outside and added to the sample, so collecting any 



1 Hardy, A. C, "A New Method of Plankton Research", Nature, cxviii, p. 630, 1926. 



2 Hardy, A. C, Min. Agric. Fisheries: Fishery Invest., ser. ii, vin, no. 7, 1926. 



