112 



Journal of Applied Microscopy. 



The net here described presents no 

 striking features of originality. It is the 

 result of some experience in pelagic col- 

 lecting, is inexpensive, durable, and so 

 constructed as to facilitate the removal 

 of the catch for preservation. The bag 

 of the net should be made of fine India 

 muslin, or, better still, of Swiss silk 

 bolting cloth. The latter is to be pre- 

 ferred on account of its greater eveness 

 and durability. This bolting cloth comes 

 in tv/enty-four different weaves, num- 



Fig. 2. 



bered from 0000 to 20, containing, ac- 

 cording to the manufacturer's state- 

 ment, from 324 to 29,929 meshes per 

 square inch. These cloths may be ob- 

 tained from dealers in mill supplies. 

 Depour & 'Co.'s Anchor brand, stand- 

 ard quality, which has been used thus 

 far in plankton work in this country, can 

 be obtained from the American agent, 

 R. P. Charles, 13 South William street, 

 New York city, or from B. F. Gump, .53 

 South Canal street, Chicago, 111. 



The No. 12 cloth is not so expensive 

 as the finer weaves and serves very 

 well in a tow net. Its meshes are not 

 so fine as to clog quickly and then push 

 aside the most of the water which the 

 net meets. In the same length of haul 

 a net of this silk will catch a great deal 

 more plankton than one made of the 

 finer silks, the greater loss by leakage 



being more than compensated by the 

 greater amount of water strained. The 

 smaller organisms which escape through 

 the silk may be secured by filtering the 

 water through hard-pressed filter paper, 



Fig. 3. 



No. 575 Schleicher & Schuell being an ex- 

 cellent paper for this purpose. Before 

 cutting out the net, the silk should be 

 boiled in soap-suds, and then pressed, 

 or, better still, put through a mangle, so 

 as to avoid the distortion of the net 

 caused by the shrinkage of the new cloth 

 with use. 



Fig. 4. 



Two nets, twelve inches In diameter 

 and of convenient length, can be made 

 from a yard of the silk, which, before 

 shrinking, is forty inches in width. In 

 cutting out the nets, the shrunken cloth 

 should be doubled lengthwise (with the 

 warp) and along a diagonal line passing 

 from "A" to "B," as shown in Fig. 1. As 

 one of the nets "D" must have two seam?, 

 an allowance of one-fourth inch must be 

 made for the extra seam. The tops of 

 the nets are marked off by striking 

 arcs across the ends of the cloth with a 

 radius equal to the length of the cloth, 

 and from "A" and- "B" as centers. The 



