968 EEPOET OF COMMISSIONER OF, FISH AND FISHERIES. [4] 



as here described, of a depth of from 10 to 18 inches, and in which were 

 growing nyrnjphcea and other aquatic plants, although exposed all day to 

 the heat of the summer sun, the temperature of the water never rose 

 above 50° to 60°, except to from 2 to 3 inches from the surface. And j 

 while the water was swarming with young fish there was no sign of op-| 

 pression to their respiratory organs, while in an aquarium tank, out in 

 the open air in the shade, with a much smaller number of fish propor- 

 tionately, the temperature of the water was always about that of the] 

 atmosphere, and the fish showed signs of more or less oppression] 

 throughout the day. 



Many of the lower forms of life, such as the chelonians, batrachians, 

 ophidians, &c., require sand patches or mossy rockeries, in which to 

 deposit their ova and in which their natural food may propagate and 

 be sought for by them. It is these conditions, so easily obtainable, 

 which produce contentment and the normal discharge of the natural 

 functions which are the subject of the biologist's investigations. 



Fronts of glass might be of advantage in these aqua- vivaria in some 

 cases, but are not generally necessary ; the only objection to them, 

 however, is the extra expense entailed without adequate advantages. 

 With the graduated depths of water, the natural and healthy growth 

 of plants, the natural distribution of light and temperature, and thei 

 pure and clear water obtainable by these methods, there is no difficulty 

 in observing the habits of animals, as they soon lose their timidity wheii^ 

 accustomed to the presence of man. 



Plates II and III will serve sufficiently well to illustrate more elabo- 

 rate forms of aqua-vivaria or combinations of such as the greenhouse 

 plan, showing adaptations absolutely impossible with the aquarium 

 tank for diverse forms of life. Eockeries properly constructed to pre- 

 vent the escape of animals, mimic waterfalls, beds of mosses, or grasses 

 and ferns, combine in such close imitation of nature that the animals 

 readily accept them as habitats. Water may be supplied by runnings 

 a pipe above with a cock for each basin, thus making each basin in- 

 dependent of the others. It may be introduced without agitation, or 

 made to tumble over rock-work, or it may be supplied at one end and 

 made to circulate through an entire series of basins by making a trough- 

 like connection between the basins with wire-gauze guards. A pipe 

 may be inserted in the bottom of each basin, with a stop-cock outside 

 for emptying the basin speedily when desired. With an elevated res- 

 ervoir, and windmill or other power to pump back the waste water, am 

 economical aqua-vivarium might be had. These methods are alike 

 adapted to the simple wants of the individual specialist or to the mul- 

 tifarious requirements of the greatest university. 



The question of food is fully as important as are those of light and 

 temperature. Many fish and reptiles will refuse all food which they do ; 

 not kill themselves. Others will feed readUy on dead animal food. 

 Others, again, will thrive upon prepared vegetable or farinaceous food. 



