PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS. 219 



framing) but also of facilitating the classification of Objects in groups, 

 and of enabling any particular series to be transported without risk of 

 injury, every slide being lodged in its own receptacle. Further, when pro- 

 vision has to be made for slides requiring greater depth than usual (such, 

 for instance, as extra-thick wooden slides, or glasses bearing deep cells), 

 trays can be made can be made either of double the usual depth, or in the 

 proportion of 3 to 2 (two such trays equalling three ordinary ones in thick- 

 ness), so as still, by keeping the case filled, to prevent shake to its 

 content when it is carried. {Smaller Slide-cases of the same kind, con- 

 taining from two to six trays, each of which holds six slides, are made for 

 the pocket. 



Section 3. Collection of Objects. 



215. A large proportion of the objects with which the Microscopist is 

 concerned, are derived from the minute parts of tfrose larger organisms, 

 whether Vegetable or Animal, the collection of which does not require any- 

 other methods than those pursued by the ordinary Naturalist. With 

 regard to such, therefore, no special directions are required. But there are 

 several most interesting and important groups both of Plants and Ani- 

 mals, which are themselves, on account of their minuteness, essentially 

 microscopic; and the collection of these requires peculiar methods and 

 implements, which are, however, very simple, the chief element of suc- 

 cess lying in the knowledge where to look and what to look for. In the 

 present place, general directions only will be given; particular details 

 relating to the several groups, being reserved for the account to be 

 hereafter given of each. 



216. Of the Microscopic organisms in question, those which inhabit 

 fresh water must be sbught for in pools, ditches, or streams, through 

 which some of them freely move; whilst others attach themselves to the 

 .stems and leaves of aquatic Plants, or even to pieces of stick or decaying 

 leaves, etc., that may be floating on the surface or submerged beneath it; 

 while others, again, are to be sought for in the muddy sediments at the 

 bottom. Of those which have the power of free motion, some keep near 

 the surface, whilst others swim in the deeper waters; but the situation of 

 many depends entirely upon the light, since they rise to the surface in 

 .sunshine, and subside again afterwards. The Collector will, therefore, 

 require a means of obtaining samples of water at different depths, and of 

 drawing to himself portions of the larger bodies to which the microscopic 

 organisms may be attached. For these purposes nothing is so con- 

 venient as the Pond- Stick (sold by Mr. Baker), which is made in two 

 lengths, one of them sliding within the other, so as when closed to serve 

 as a walking-stick. Into the extremity of this may be fitted, by means 

 of a screw socket, (1) a cutting-hook or curved knife, for bringing up por- 

 tions of larger Plants in order to obtain the minute forms of Vegetable or 

 Animal life that may be parasitic upon them; (2) a broad collar, with a 

 screw in its interior, into which is fitted one of the screw-topped Bottles 

 made by the York Glass Company; (3) a ring or hoop for a muslin King- 

 Net. When the Bottle is used for collecting at the surface, it should be 

 moved sideways with its mouth partly below the water; but if it be 

 desired to bring up a sample of the liquid from below, or to draw into 

 the bottle any bodies that may be loosely attached to the submerged 

 plants, the bottle is to be plunged into the water with its mouth down- 

 wards, carried into the situation in which it is desired that it should be 

 filled, and then suddenly turned with its mouth upwards. By unscrew- 



