and Laboratory Methods. 



1407 



a weight at the apex of the cone, either formed by melted solder poured in, or 

 by a lead weight which may be tied to the interior of the cone or to the screw- 

 cap. In dragging the net along the bottom, I prefer to have the cone and net 

 without weights and to attach a weight to a line so long that it will drag a little 

 way behind the end of the dredge. In this way the net draws over the bottom 

 instead of digging into it, as it is apt to do if weighted at the apex. 



The materials and construction of the apparatus are such that it can be con- 

 structed by any tinman, and nets can be made of any size for various purposes. 

 I have used them up to six inches in diameter and with a cone provided with a 

 quarter-inch mesh. Such a net was used for collecting in salt water, to prevent 

 the entrance of floating algae. In nets so large it is well to make the cone top 

 in two pieces so that the net can be easily removed from the cone. 



In collecting on expeditions where it was not convenient to carry a large 

 number of small bottles, I have furnished little bags of such a size as to slip 

 over the spout of the funnel. The material collected is washed out into these 

 bags, which are tied, numbered and labeled and placed in a large bottle or can 

 of preserving fluid. E. A. Birge. 



University of Wisconsin. 



A Modification of the Birge Collecting Net. 



To collectors of the smaller aquatic organisms, especially of such as Crusta- 

 cea, Hydrachnidae, etc., the Birge collecting net, or some similar apparatus, is an 

 indispensable part of their equipment. The 

 writer has used it with general satisfaction 

 for several years in the collecting of water-mites. 



There are occasions, however, when its use 

 in the ordinary form becomes awkward or im- 

 possible owing to the place or conditions about 

 the place where it is desired to make collections. 

 Frequently it is desirable to secure material 

 from narrow, tortuous streams in which a straight 

 haul for any distance is impossible, or from small 

 springs or pools, or from the shore when, owing 

 to the uncertain footing or to the interposition 

 of branches or other objects, casting is extremely 

 difficult, or in water so choked with vegetation 

 that only small open spaces are left here and 

 there amongst the weeds. To meet such condi- 

 tions the author devised and has put to successful 

 use the following modification, which he ventures 

 to suggest to others who may have felt a similar 

 want. 



Briefly stated, it is as follows : A groove 

 (Fig. 1) is passed about the tin cylinder. 



