526 PREPARATION, MOUNTING-, AND COLLECTION OF OBJECTS 



of their minuteness, essentially microscopic; and the collection of 

 these requires peculiar methods and implements, which are, however, 

 very simple, the chief element of success lying in the knowledge where 

 to look and what to look for. In the present place, general direc- 

 tions only will be given ; the particular details relating to the several 

 groups being reserved for the account to be hereafter given of each. 

 Of the microscopic organisms in question, those which inhabit 

 fresh water must be sought 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, &c., that may be floating on the surface or sub- 

 merged 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 convenient as the poml- 

 stick, 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 portions 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 ring-net. When the bottle is used for collecting at the sur- 

 face, 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 

 altached to the submerged plants, the bottle is to be plunged into 

 the water with its mouth downwards, carried into the situation in 

 which it is desired that it should be filled, and then suddenly turned 

 with its mouth upwards. By unscrewing the bottle from the collar, 

 and screwing on its cover, the contents may be securely preserved. 

 The net should be a bag of fine muslin, which may be simply sewn 

 to a ring of stout wire. But it is desirable for many purposes that 

 the muslin should be made removable ; and this may be provided 

 for by the substitution of a wooden hoop, grooved on its outside, for 

 the u ire ring; the muslin being strained upon it by a ring of 

 vulcanised indiarubber. which lies in the groove, and which may be 

 readily slipped oft' and 011. so as to allow a fresh piece of muslin to be 

 put in the place of that which has been last used. At the end of the 

 muslin bag is tied a small rimmed tube-bottle of thin clear glass 

 three inches long by one inch in diameter. In this, objects can be 

 fairly seen. The collector should also lie furnished with a number 

 of bottles, into \\hich he may transfer the samples thus obtained, 

 and none are so convenient as the screw-topped bottles made in all 

 si/.es 1>\ the York (Jlass Company. It is well that the bottles should 



