da ON THE ANIMALCUL.E OCCURRTNG IN A DROP OF WATER. 



scarcely observe, that the corks must be taken out as soon as the water is 

 brought home. It is best also not to keep the bottles in the full light of 

 the sun. A label should be affixed to each bottle, with the date and locality 

 from whence the water was procured. This is very necessary, for each bottle 

 may aflPord employment for several weeks, and as water from different ponds 

 will probably be procured, much confusion woxild otherwise result. In preparing 

 the water for examination by the microscope, the plan I usually adopt is, to 

 take a piece of flatted window glass, three inches long, by one or one and 

 a half wide, according to the size of the object to be examined. Having 

 then placed on the glass a small portion of the duck-weed, or grass, a single 

 drop of water is to be added, and a piece of paper, having a hole cut in its 

 centre, being placed on the glass, the whole is to be covered with another 

 plate of thin glass. These glasses being now placed under the spring clips on 

 the stage of the microscope, will be kept in position, and the paper will prevent 

 the glasses crushing the objects. Should the microscope not be provided with 

 a spring clip, it may be easily added, or some equivalent substituted. It is 

 seldom that more than a single thickness of paper is required, unless for the 

 examination of some of the Entomostraca, which, being of considerable size, 

 often require several thicknesses to prevent crushing. I may just add that the 

 water is kept in its position by what is called capillary attraction, and is not 

 touched by the paper. 



We now come to the actual investigation of the contents of the drop of 

 water. In doing this, the best way is to commence with a low power, say an 

 inch, which will magnify about sixty times, or at most half an inch, which 

 wiU magnify, say two hundred times. In saying that an object is magnified sixty, 

 or two hundred times, we do not perhaps obtain a just idea of the fact, which 

 is, that it is made sixty, or two hundred times longer and broader, or in reality, 

 that it is magnified three thousand six hundred, and forty thousand times 

 respectively. This gives you an opportunity of taking a general survey of the 

 whole field in a short time; and should there be nothing of interest on- the 

 slide, you can change the drop, and try again. Should, however, any matter 

 of interest appear, you should move it as near the centre as possible, and 

 then change the inch power for a higher one, say quarter of an inch. If the 

 object was fairly in the centre of the field, you will now probably find it 

 somewhere in sight; if not, you must move the slide about till you find it; a 

 slight movement will generally be svifficient. 



Having thus disposed of these preliminary matters, I will now as briefly as 

 possible describe the various living forms observed in the Askham bog water 

 last June; but first, I may remark that the whole of the Infusoria may be 

 divided into two great classes — 



First. — The Polygastrica, from their presenting the appearance of having 

 numerous small stomachs connected with the intestinal canal. The Animal- 

 culae of this class are of an apparently less complicated structure than those 

 which compose the Second division, namely the Botifera, or Wheel Animalculae, 



