428 Birge — Vertical Distribution of Pelagic Crustacea. 



hanging the weight-hangers on the weight-pins — which occu- 

 pies hardly a second for each weight. 



The bucket. — The bucket consists of three parts, the bucket 

 proper and the two pieces by which it is attached to the bag. 

 (Plate VII, figs. 2, 3.) Each is made of thin spring brass. The 

 two attaching pieces are cylinders. The upper one fits into the 

 lower, and is about 6 cm. in diameter and 5 cm. deep. It has a wire 

 to stiffen it in the upper edge. This and all of the parts are lap- 

 soldered, so as to avoid a seam. The second or lower cylinder is 

 large enough to fit over the upper one, and to permit the net to 

 come between them. Each is provided with three equidistant 

 loops of wire, by which they may be fastened together, and 

 the lower one has two pins on opposite sides which fit into the 

 ba} 7 onet catches of the bucket. The dredge net is drawn down 

 inside the upper cylinder and turned up over its exterior; the 

 lower cylinder is slipped over it and fastened to the upper one. 

 The mouth of the net is thus held firmly between the cylinders, 

 and at the same time no projections are left to hold back its 

 contents, nor are there any longitudinal folds, if the dredge-net is 

 properly fitted to the cylinder. The bucket proper is a cylinder 

 of thin brass 6 cm. in diameter and 7-J cm. high, with four 

 windows in its lower part, each 3^ x 4 cm., covered with brass 

 wire gauze of .01 inch mesh. The opening of each mesh is 

 about 0.17 mm. (.007 in.) in diameter. In the upper edge are 

 ■cut notches for a bayonet catch, by which it is attached to the 

 middle cylinder. It slips over the middle cylinder for a dis- 

 tance of 3 cm., thus securing a tight joint, so far as the Crust- 

 acea are concerned. The bottom is slightly conical, and leads 

 to a conical tube filled by a rubber stopper, which is put in by 

 a wire handle from the inside. There are three legs upon which 

 the bucket may stand. In Fig. 2 the upper cylinder is sup- 

 ported by blocks upon the second one. 



The dredge as described abovt is not to be considered as an 

 attempt at a universal self-closing dredge. It was designed to 

 meet the conditions of the special problem which we had pro- 

 posed and was found to meet those conditions admirably. 

 The advantages of the dredge appear to me to be as follows: 



(1) It is simple, easily worked, and reliable. 



