Cyclopidae 227 



ALGAL CULTURES 



Ankistrodesmus, or other unicellular alga. Culture methods may be 

 found in botanical texts, but we have had best results with rich cultures 

 of Ankistrodesmus that have developed naturally in aquaria in the 

 laboratory in which small fish have been kept and fed with fish roe 

 or in cladoceran cultures kept in bright sunlight and fed with small 

 quantities of sheep manure infusion. The green water from the 

 aquarium is passed through filter paper and kept in covered jars 

 for observation during several weeks to guard against the presence 

 of wild copepods. Occasional fertilization of these clean aquaria with 

 sheep manure or with liquid fertilizers in small quantity may be de- 

 sirable. 



Moitgeotia. A small dense tuft of the filamentous alga, Mougeotia, 

 is held over a watch glass of water while successive close choppings are 

 made with a scissors. This food medium then consists of short fragments 

 of algal filaments, extruded protoplasm and water ; after stirring, a few 

 drops may be used in place of the unicellular algae. Results have been 

 excellent in growth and fertility of the Crustacea. 



CYCLOPS 



The amount of medium to be used and the frequency of feeding depend 

 upon temperature and conditions of the experiment. In our practice a 

 female with sacs is placed in a small vial with about 3 cc. of filtered 

 pond or aquarium water and 1 cc. of mixed food (Protozoa with a little 

 algae). As the manure cultures become older, dilution with pond water 

 may be unnecessary. The culture water is changed or supplemented 

 about every two days at 23 C. or about every two weeks at 6° C. The 

 condition of the culture water may be appraised, and the need for sup- 

 plemental feeding determined by looking through the vial toward a 

 light; the liquid should neither appear cloudy nor have the excessive 

 clearness indicative of food deficiency. Adjust feeding to maintain a 

 reasonable abundance of Protozoa, evident to the eye, and a suggestion 

 of greenness in the liquid or on the bottom of the vessel. Nauplii in 

 quantity may be kept in larger containers with about 4 cc. of medium 

 per nauplius and, if required, one or two supplemental feedings in the 

 course of development. 



The methods employed have given maximum rates of growth (com- 

 plete life cycles for C. vernalis in 7 days), high fertility through several 

 generations, and virtually no disease or fungus. Copepods reared in the 

 protozoan cultures without algae have lived well, and in many cases have 

 grown rapidly, but they have displayed greater individual variation in 

 rate of growth and less fertility than those given some plant food. 



