292 Tue MICROSCOPE. 
through which the water passes after it has been poured into the 
unobstructed outer funnel, the claim being that the microscopic 
animals are retained in the bottle in ever increasing numbers. 
These are good in theory but not so successful in practice. If 
the strainer is fine enough to retain the minute creatures, the 
water passes slowly or not at all; if coarse enough to allow free 
passage to the water, the meshes must be so large that only the 
larger microscopic animals will be retained. And with most of 
them the strainer becomes so clogged by dirt that it is practi- 
* cally water tight, the water poured in simply rushing over the 
sides of the outer funnel without entering the vessel. 
Another method is to drill near the bottom of the bottle, a 
series of holes over which a strip of fine muslin is tightly 
applied so as to act as a strainer. This has the same objection- 
‘able features as the more elaborate contrivances of the dealers. 
The wet muslin allows the water to trickle through it with vex- 
atious slowness, retaining more dirt and extraneous matters than 
_ animals. I have tried all these things, and have discarded them 
for the simple glass fruit jar and the tin dipper. 
With the dipper the bottle is filled, and allowed to stand on 
the table near the window for a few days, when the Infusoria 
will increase in a surprising manner. But the bottle’s contents 
-y should be examined immediately, for although many forms that 
will not be in the gathering when first made, will develop there in 
a short time, and others will die and melt away almost as soon, 
The collection should therefore be examined with the micros- 
cope as soon-and as often as possible, for the curious rule is that 
certain animal forms will abound and flourish for a while, seem- 
ing to appear quite suddenly, only to disappear almost as sud- 
. denly, giving place to others of different form, character and 
habits. The food supply acceptable to one kind may become 
exhausted, and the environment agreeable and beneficial to that 
form may become so changed that some are killed either by 
- starvation or unpropitious surroundings, while there may be 
present an abundance of nutriment specially needed by the 
other kinds that so speedily succeed those that have died; in- 
deed, the diffluent bodies of the latter may furnish the food 
demanded by their successors. But why it is that one class'will 
{die out to be followed by another, cannot be positively known. 
_ The fact, however, remains, and the microscopist in order not to 
