330 University of California Puhlications in Zoology. [Vol.8 



side of the cable from the trip. This stop is adjustable and 

 absorbs the shock of the messenger as soon as the trip is driven 

 down sufficiently to release the jaw of the net. 



The messengers are of two distinct types. The first mes- 

 senger (pi. 22, fig. 1) is cylindrical, about 9 by 11.5 cm. and 

 w^eighs about 4 kilos. Its diameter is just sufficient to strike the 

 pin of the trip which releases the lower jaw and thus opens the 

 net (pi. 22, fig. 2). The second messenger is provided with fo^^r 

 spreading arched arms which carry a distal ring which drops 

 over the first messenger and strikes the trip which releases the 

 upper jaw and closes the net (pi. 23, fig. 3). Its total length is 

 30 cm. and greatest diameter 15 cm. and its weight about 8 kilos. 

 Both messengers are made in halves which may be lashed 

 together about the cable. The first messenger requires but a 

 single lashing, the second two, one in each of the groves at each 

 end (pi. 23, fig. 3). The greater length of the second messenger 

 not only provides for overriding the first but it also tends to 

 obviate anything but a square blow upon the tripping pins. The 

 messengers may be lined with Babbitt metal to take up wear, 

 as in the Arntzen detachable messengers used on my (1906) 

 self-closing water-bucket, if desired. 



THE NET AND PLANKTON BUCKET 

 The net proper is a simple conical bag of any desired stuff, 

 preferably of silk bolting-cloth, with head-piece and bucket band 

 of butcher's linen. The bag is fastened to the jaws by brass 

 strips or closing bands (cl. hd., pi. 25, fig. 13) held in place by 

 numerous screws set into the inner face of the jaws. In the 

 case of the finer silks, such as nos. 12 to 20, it is important to 

 make the bag as long as possible, up to 2 meters. 



To keep the bag from becoming entangled in the tripping 

 device or about the cable, a supporting rod (n. sup., pi. 25, fig. 

 15) 1.5 to 2 meters long, made in three sections, with distal end 

 curved downwards (pi. 23, fig. 4) is attached to the rear of the 

 head-piece of the frame. It carries a coiled spring at its outer 

 end which connects it with the bucket which in turn is supported 

 by a wire hook to the rod above it. The proximal end of this 



