STATE GEOLOGIST. 177 



and then poured into a thin filter-paper or a thin muslin bag. 

 When nearly dry, the funnel is held over a small bottle, an open- 

 ing is made in the apex of the filter, and the contents washed 

 through with slightly dilute glycerine. Soon after pure glycerine 

 is added so as to bring up the whole to the required degre of con- 

 centration. A sufficiency must be used to well cover up the whole. 

 In case of haste the end of the filter containing the gathering may 

 be torn ofi*and placed at once in a bottle of glycerine or alcohol. 



For the collection of Cypridae it is recommended to use a very 

 thin fine net, and gather as much as possible of the finely commi- 

 nuted debris which settles in weedy pools. Spread this material in 

 shallow pans and in an hour or so skim the surface with a small 

 spoon-like hand-net, and transfer with the addition of clear water 

 to shallow porcelain plates. Such sfatherings may contain Ilyo- 

 cryptus, Monospilus, the hook-nosed Pleuroxids (=Percantha) and, 

 perhaps, also species of Canthocamptus. 



The entomostraca of the larger lakes must be sought by a differ- 

 ent method. A net of larger size, and composed of very thin ma- 

 terial is drawn after a boat which is kept moving in different parts 

 of the lake. Such a net should be so weighted as to receive water 

 from the surface as well as from several inches below it. The net 

 is emptied occasionally with plenty of water into large bottles, 

 which may preferably be placed in the dark if to be unexamined 

 for some time. Water kept in the dark will preserve its animal 

 life for a much longer time than if exposed to the sunlight. 

 m. A similar net may be placed in a rapid stream in such a way 

 that it remains partly full, but does not overflow. The accumula- 

 tions of a day may be thus gathered into little space. The faucets 

 of the city water will frequently afford a good supply of animal 

 life, and unfortunately in Minneapolis a rather large number of 

 forms are worms of a suspicious and unpleasant appearance. It 

 must be observed that for this purpose the faucet must be well 

 open so that a good current is secured, otherwise most of the im- 

 purities will be dropped on the way. A friend mentioned that very 

 little life was found in the city water after long and careful experi. 

 ment, during which, however, a very small stream was allowed to 

 trickle through the complicated set of graduated screens. But the 

 writer at the same time secured a rather large supply both of en_ 

 tomostraca and vegetable forms by simply permitting the water 

 from the hydrant faucet to flow with full head through a muslin 

 net. 



But our methods are not yet exhausted. The dipping bottle 

 12 



