208 Phylum Arthropoda 



in manure solutions) seem to be best; and live bacteria appear to be 

 essential (Stuart, McPherson, and Cooper, 1931). 



The manure solution or "stable tea" to be described below has, in the 

 writer's experience, proven a most satisfactory culture medium. It would 

 be misleading, however, to encourage the worker to think that this cul- 

 ture medium is infallible and that every make-up of medium is equally 

 good. It is, however, a highly successful method. 



The manure solution or stable tea medium may be made up in accord- 

 ance with either of the following formulae in battery jars 9 inches in 

 diameter by 12 inches high or in stone jars or enameled containers 

 approximately that size. Galvanized or copper containers are to be 

 avoided for handling the pond water inasmuch as zinc and copper are 

 extremely toxic to Cladocera. 



Formula I. Garden soil 2 lb. 



Horse manure 6 oz. 

 Pond water 2^2 gal. 



The ingredients should be placed in the container in the order named. 

 The container may be kept in a cool place or surrounded by running 

 water to keep the temperature 15 to 18 C. After 60 to 72 hours (or 

 48 hours if the temperature has been higher) the floating manure, if any, 

 is removed and the super-natant liquid strained through a silk bolting 

 cloth (about 130 meshes per inch) or other similarly porous, smooth- 

 threaded cloth. With the final liter or so of the liquid a quantity of 

 silt is placed within the straining cloth and enough silt is worked through 

 by active stirring or gently rubbing through the cloth to produce in 

 settling a layer of sediment 1 or 2 mm. thick on the bottom of the jar. 

 This strained liquid constitutes the stock medium. It requires dilution 

 with pond water before being used as culture medium. The proper 

 dilution may vary between 1 part of the stock medium to 2 to 4 parts 

 of pond water, depending upon the density in appearance of the liquid. 

 The pond water used both in making up the stock medium and in the 

 dilution of it is strained or filtered to avoid contamination with "wild" 

 Cladocera and copepods.* 



The horse manure may be obtained from a stable and allowed to age 

 for a week or ten days before use. Fresh manure, dry or moldy manure, 

 or manure more than a month old is ordinarily to be avoided. It is con- 

 venient to keep a small supply covered over in a wooden box or cardboard 

 carton, which may be kept outdoors (but sheltered from rain) or in a 

 basement location. The stock medium in process of ripening and the 



*Tap water has frequently been used after it has stood in an aquarium containing some 

 fine sand or silt for at least a week or ten days. But it is questionable if tap water which 

 has been heavily chlorinated or subjected to other extreme measures to render it potable 

 may be so readily "conditioned" and thus rendered suitable for such use. 



