AQUARIA FOR MICROSCOPIC LIFE. 137 



to be troublesome, set the jar in a dark closet for a few days and 

 they will disappear. 



However, for microscopic purposes, such growths are not 

 usually objectionable, for some of the Infusoria delight in them, 

 and it is not necessary to keep the sides of the small bottles clear, 

 as in the case of larger aquaria. Nevertheless, they should not be 

 allowed to increase too much, for if they do they may suddenly 

 fill the water with a cloud of swarmspores, and bring about a de- 

 composition which will kill everything therein. Such a condition 

 of affairs, if threatened, can be prevented by removing the jar a 

 short distance from the window, when growth will be less rapid. 



It does not seem to be a matter of much consequence what 

 plants are used in the microscopist's aquaria. Nitella is a clean 

 and hardy plant, and we have usually preferred it. One or two 

 stems, a couple of inches long, is enough. Anacharis is also 

 excellent for the purpose ; Myrio;phyUuni would doubtless prove 

 quite as good, and perhaps even better, for it is a plant with 

 leaves well adapted as a resting-place for the tube-bearing rotifers. 

 Besides these we have Ceratophylliwi^ Caliitriche, Utricidai'ia^ 

 NaiaSj and FotaftiogetOfi ; but some persons prefer Ceratophyllum 

 above all other plants for the aquarium. 



As for the stocking of small aquaria, the only precautions are, 

 not to put in too much material, and not to put in animalcules 

 that will kill each other. Our plan is as follows : — When we have 

 a collection of pond-life, plants, and animals of all kinds all 

 together, we put the whole mass into a saucer of water and let it 

 remain there until it is convenient to look it over. In a saucer 

 the collection will keep fresh, while in a bottle it would soon 

 become foul. Then, in looking over it with the microscope, the 

 animalcules that it is desired to keep are transferred to the bottles, 

 either by washing them off from the slide upon which they are 

 found, or, if practicable, by the use of a dipping-tube. But a 

 mass of algae or of debris that is supposed to contain infusoria of 

 interest is not introduced at random. Such a mass may be 

 dropped in for a few hours and then removed by forceps or dipping- 

 tube ; but it must not remain long enough to decompose. This 

 should never be done in a bottle that already has a variety of 

 living forms in healthy growth, as thereby there is danger of losing 

 them by introducing incompatible creatures. 



Sometimes it is desirable to keep a certain specimen found in 

 a jar attached to something, as a leaf or stem, separate from the 

 others for a short time. This can readily be done by placing it in 

 a small tube, uncorked, which can be suspended in the jar by 

 means of a thread, or by a bit of sheet-cork with a hole cut 

 through it. In the same way a number of specimens can be 



