Various invertebrate animals. 107 



the "Bulletin of the U.S. Nat. Museam," 1892, Vol. XXXIX., 

 Pt. G, pp. 26-30. If a ready-made naturalist's dredge has not 

 been obtained, the apparatus can be made by a blacksmith. A 

 good average size for moderate depths is 20 inches by 5 for the 

 frame, and 2 feet length for the net. Dall recommends that a 

 frame of galvanized iron should be riveted on near the back 

 edge of the iron frame, and the canvas and net laced with copper 

 wire into holes in the galvanized iron ; thereby the bad effects of 

 iron rust on the net are avoided. The upper and lower outer edges 

 of the frame are bevelled to enable the dredge to catch along the 

 bottom. The rope is attached to the ring of only one of the arms, 

 the two arms being fastened with cord. The object of this is to 

 lessen the risk of losing the dredge if it gets fixed among rocks ; when 

 this hajjpens the cord bi*eaks, thus allowing the arms to separate 

 and the dredge to be released. It may be necessary to fix a weight 

 on the rope about 10 feet from the mouth of the dredge, in order 

 to keep the edge of the frame along the bottom. The length of rope 

 required for small depths is equal to about twice the depth. The 

 feel of the rope is the best indication as to how the dredge is working. 



When the dredge is hauled up, delicate specimens should be 

 picked out before disturbing the contents. To separate specimens 

 from the mud and fine sand, place tlie dredged material in a sieve 

 and rotate it in a tub of water. Any very small specimens that pass 

 through the sieve can be secured later by gently stirring up the mud, 

 pouring off the liquid, and adding more water. After this process 

 has been repeated a few times, the mud is washed away, and the 

 specimens will then be seen lying at the bottom. 



A tangle is useful for catching up spiny specimens. The apparatus 

 consists of an iron bar, straight, or bent at a right angle, and with 

 five or six pieces of chain attached to it. Untwisted strands of rope 

 are attached to the chain-links. 



Towing-net. — A to wing-net * is used for surface or pelagic animals, 

 A conical net of cheese-cloth, bolting-cloth, or coarse- woven bunting, 

 about 2 1 feet in length, is fastened to a copper ring about 1| feet in 

 diameter ; it is best to double a strip of cotton cloth round the ring, 



* Fine silk for riankton-nets may be obtained of Mr. Frechter, Baltic 

 Buildings, Red Cross {Street, Liverpool. 



