750 THE MICROSCOPE. 



THE EXAMINATION OF RIVER-WATER. 



At the present time, the Thames basin drains more 

 than two and a half million acres of land, the greater 

 portion of which is highly cultivated and heavily 

 manured. It might be safely predicted, on taking 

 specimens of water from any part of the river, that it 

 will contain organic impurities, in suspension and solu- 

 tion. A bottle of Thames water, taken near Windsor 

 in the spring of 1881, abounded in various species of 

 animal life. On standing the bottle in the light, in a 

 very short time a considerable sediment was deposited, 

 consisting of vegetable, animal, and mineral matters. 

 On removing a drop with a pipette, and placing it 

 under the microscope, numerous portions of conf'ervae, 

 diatoms, decaying vegetable matter, the outer cases 

 of entomostraca, &c., were visible, and apparently only 

 very few of the minuter kinds of animal life. Allow- 

 ing the water to stand by some forty-eight hours, ex- 

 posed to light and warmth, another dip was taken, and 

 a higher magnifying power used, when a number of 

 embryos were seen moving about the field, the more 

 noxious of which were minute filiform nematode w r orms, 

 Chcetogaster lymnceus, Anguillula fluviatilis, Hydra 

 ftisca, Thames mud-worm, Cyclops quadricornis, Daplinia 

 pulexj Paramoecium, pupa of culex, bacteria, &c. 

 Now, considering how little the Thames had been dis- 

 turbed by floods or rains during the previous three or 

 four weeks of April and May, it must be admitted that 

 this small quantity of water, containing, as it did, the ova 

 and embryos of animals, constituted a serious amount of 

 contamination. The habits, or rather the natural his- 

 tory, of some of these creatures are well worth a careful 

 examination. First, nematode worms ; these have 

 obtained an unenviable notoriety amongst the greater 

 pests of animal life. The typical form of filarian 

 worms is the thread-worm : this affects human beings, 

 sheep, and other ruminants, as well as several kinds of 

 birds. There are eight or ten different kinds belonging 

 to the genus, and some of which, like Fasciola hepatica. 

 fluke, change their hosts once or more before attaining 



