420 BIOLOGICAL STUDY OF TAP WATER. 



There are Leptothrix forms besides the ordinary Cladothrix 

 filaments, which, by the breaking np of the threads, produce micro- 

 cocci and rod-like forms. The cocci are circular in outline, and have 

 a diameter equalling, or at most double, that of Micrococcus pro- 

 digiosus, Cohn. In from 24 to 48 hours these micrococci develope 

 into rod-like forms (Bacterium, Bacillus), which again give rise to 

 Leptothrix, and by branching to Cladothrix filaments. These 

 filaments are often rolled into a loose spiral, and these spirals give 

 rise to Vibrios, Spirillum — and Spirochaete — forms. All the forms 

 already mentioned may pass into a zooglaea or resting stage. 



Beggiatoa alba goes through pretty much the same modifications. 

 There are Leptothrix-like filaments of considerably larger size than 

 those of Cladothrix dichotoma, Bacillus, Bacterium, and Micrococcus 

 forms. Spiral forms are also developed, which however I have never 

 seen in any of the sediment I examined, all the spiral forms noticed 

 having been referred to Cladothrix. 



In the study of these organisms it will be found of great advantage 

 to stain them first with rose-aniline, or iodine. 



Before proceeding to enumerate the species belonging to the 

 Animal Kingdom, a form must be described which I am puzzled to 

 know where to locate. I have only noticed it occasionally ; and I 

 am inclined to regard it as a Desmid. 



The body is spheroidal, in optical section broadly oval, surrounded 

 by a firm cytioderm ; color, bright green ; chlorophyll, disposed in 

 two lenticular masses ; vacuoles, four ; body surrounded by 7 — 9 (?) 

 stiff, colorless, more or less curved bristles (setae), coming off radially, 

 and 3 — 5 times the long diameter of the body in length. Three 

 individuals gave the following measurements : — 



Diam. (1). 0-0093 mm. by 0.0124 mm. 

 (2). 0-01142 mm. by 0-01428 mm. 

 (3). 0-0121 mm. by 0-0154 mm. 



Habitat, Lake Ontario. Fig. 4. 



Wood describes a globular form of Scenedesmus with radiating 

 bristles, to which the organism above described is possibly allied. 



In addition to the foregoing species the vegetable kingdom is 

 represented by starch grains, spores of fungi, and occasionally some 

 remains of the higher plants, such as pollen grains, cuticle of 

 aquatic plants, woody fibre, .&c. 



