MICHIGAN \('\l)l,\n Ol SCIKNJCE. 39 



to their new environment and may be studied under approximately 

 natural eonditions. Of the animals suggested fish and tadpoles are the 

 only ones that must he fed. Prepared fish food and very small bits 

 of uneooked meat will bt- found sufiieient for them. Care should be taken 

 always to remove uneaten ))ieees of nuat as these macerate rapidly and 

 pollute the water. As jjlants become uprooted, as will surely be the case 

 if tad))oles are in the tank, they should carefully be replanted because 

 they are not only necessary to tlu' "balance" of tiic aquarium but if 

 allowed to Hoat will soon decay and become a source of contamination. 



If proper precautions and reasonable care arc observed, the balance 

 between plant and animal life will soon l)e obtained. The growing 

 plants function in the oxidation of the water and the animals contribute 

 earbondioxide and nitrogen necessary for plant growth, tiie balance 

 becomes established with the exception of the partial food supply^ and 

 when once obtained the a<piarium requires almost no further attention 

 and becomes a valuable demonstration of the interdependence of ])lant 

 and animal life. 



Should it become necessary for any reason to change the water or to 

 remove part of it to facilitate moving the tank, it can readily bi? done 

 by carefully dipping the water out or by using a small rubber tube as 

 a sii)hon. Tliis should never be done if avoidable, particularly if the 

 tank contains Hydra, as many of those adhering to the sides will be 

 killed. Tiiev may be kept alive for a brief ])eriod while water is being 

 changed, if they are not allowed to dry. 



The terrarium is e(jually valuable in the laboratory and when properly 

 constructed requires little if any more care than the aquarium. The 

 type of terrarium suited to salamanders, frogs and animals requiring 

 similar environments only, will be considered here. The same types of 

 tanks may be used as for the aquaria. If a sufficient quantity of gravel, 

 that is, a layer at least an inch thick is used for the foundation, a drain- 

 age outlet will be found unnecessary. The gravel may or may not be 

 followed by a layer of sand, l)ut a layer of mixed leaf-mold and soil 

 must be used as a rooting place for the moss, ferns and other plants 

 introduced. Here also care must be exercised in the selection of animals, 

 although there is less danger from crowding tlian in the ease of the 

 aquarium. Small frogs will be eaten by large ones; snakes, even small 

 ones, arc more or less unsatisfactory when kept with otiier animals 

 and if collected should have a tank or cage separate from them ; terrestial 

 snails are easily obtained and live harmoniously together; small salaman- 

 der, particularly Diemi/ctylus viridescens, make very satisfactory inmates, 

 the Ambystomas, however, should be in a separate terrarium where thev 



