178 SELECTION AND TTSti 



wheel animalcules and Entomostraca, or water fleas, they are 

 to be found in every pool. 



Every young microscopist that is desirous of pursuing his 

 studies in this direction, is met at the outset by two difficulties; 

 the first is to obtain the objects, the second is to find out what 

 they are after he has got them. The first is by no means a dif- 

 ficult task, but the second will often puzzle more experienced 

 students than those whom we expect to be readers of this book. 

 We know of but two ways to accomplish it; one is the laborious 

 plan of searching for them in the " Micrographic Diction- 

 ary," or the books of Carpenter or Pritchard; the other is 

 to obtain the desired information from some well-informed 

 friend. 



The objects which are of most interest to the microscopist are 

 not difficult to obtain, if we know where to look for them, but 

 they are not to be found everywhere. Many stagnant pools 

 will be found to yield but a scanty supply, while others, which, 

 perhaps, to the uninitiated present a less promising appearance, 

 will yield a rich harvest. Beginners are very apt to entertain 

 the popular notion, that every drop of water teems with animal- 

 cules, and that when placed under the microscope, it will appear 

 to be literally filled with living things. This idea is fostered 

 by popular writers who describe a drop of water as a globe filled 

 with life, and by lecturers who exhibit pictures and enlarged im- 

 ages of what they call "a drop of water," but which is in reality 

 a considerable quantity of that liquid which has been artificially 

 supplied with inhabitants. Clear well water is almost free from 

 microscopic organisms, and the same is true of the water from 

 clear brooks, which flow swiftly over a pebbly bottom. Ordin- 

 ary rain water, as found in cisterns having free communication 

 with the air, usually contains large numbers of the larvaa of 

 gnats and mosquitoes, and when exposed to the light it is almost 

 always rich in wheel animalcules, and some of the lower forms 

 of vegetable life. The water supplied to our cities is in gen- 

 eral very rich in microscopic vegetables. Thus in the Croton 

 water, which is comparatively pure, we have found a large 

 number of very beautiful species, amongst them the exquisite 

 Monachinus. The best way to secure a supply of the animal 

 and vegetable inhabitants of city water, is to pass a considera- 



