Methods ill Plankton Investigations. 9 



2. The Carriage (Plate III., Fig. 6 and 7). — The carriage 

 for the plankton net is a wooden bar, 100x5x2 cm. It 

 bears upon one edge two ceiling pulleys (Fig. 6,/. and /.'), 

 through which passes the carriage rope {c. r.). In order that 

 there may be no tendency on the part of the carriage to tioat, 

 two bars of lead (/.) are inserted in its lower edge, so that it 

 naturally assumes a position upon the lower side of the rope. 

 The carriage is so constructed that it may be separated along 

 the line a b e, thus freeing the net from the fixed carriage 

 rope. Its two parts are held together by two Hat brass hooks 

 {h.) which enter the staples {s.). The net and the lines per- 

 taining thereto are attached to the removable part of the 

 carriage at four points {w, .»■, y, z) at which screw-eyes are 

 inserted, the attachment l)eing made by means of small metal 

 snaps {sn.). At the anterior end of the carriage a stay-line 

 {s. I. 4), coming from the end of the draw line {d. /.), is fast- 

 ened to the screw-eye tv. Upon this line comes the main 

 stress when the carriage is drawn along the rope. The upper- 

 most of the three stay-lines of the net {s. I. 1) bears a snap 

 which is fastened to the screw-eye x at the lower anterior 

 corner of the carriage. This makes it certain that the plane 

 of the mouth of the net will be kept perpendicular to the line 

 of progress of the carriage. A snap at y binds the net to the 

 carriage and another at z supports the bucket. 



3. Accessory Apparatns (Plate III.). — The stay- and draw- 

 lines are of braided linen. The latter is about thirty-hve meters 

 in length and is carried on a hand-reel. It is knotted at inter- 

 vals of one meter to a point thirty meters from the opening 

 of the plankton net. The carriage rope is a five-sixteenths 

 inch braided rope known in the trade as " sash cord." It 

 does not kink in handling, and if once thoroughly seasoned 

 is subject to little change when wet and cannot easily be 

 stretched. This roiie is about forty meters in length and is 

 marked by colored threads at a point exactly thirty meters 

 (Plate III., Fig. 7, m.) from the opening of the net. The 

 location of the end knot (Fig. 6, k.) is marked in a similar 

 manner. 



Three sharpened stakes (Fig. 7, b. s., m. s., and e. s.), the 



