3 8o SCIENCE PROGRESS 



by the trouble and expense incurred when rapid multiplication 

 has taken place. In Germany it is known as the " Brunnen- 

 pest." Among its visitations may be mentioned Breslau in 

 1870, Berlin in 1878, Lille in 1882, Rotterdam in 1888, and 

 Cheltenham in 1896. At Cheltenham in 1896 the water sup- 

 plied to the town became red and turbid, and from it there 

 emanated an offensive odour. Within a fortnight the filters 

 had become clogged. This state of affairs continued for about 

 six weeks, after which the water once more began to assume 

 its normal appearance. In spite of this alarming state of 

 affairs Garrett reports that there was no evidence to show that 

 the organism had any pathological influence. The appearance 

 presented by an adult specimen of Crenothrix is very char- 

 acteristic, and when once seen is subsequently easily recognised. 

 This is shown in fig. 4, A. It consists of a hard cylindrical 

 sheath, narrow at the base, but widening at the top. Inside the 

 sheath are a number of short rods. When growing under 

 normal circumstances these rods in young plants are arranged 

 in a single row (fig. 4, B), but in older specimens the rods at 

 the apex tend to break up into a number of round cells or 

 " cocci " as they are called. This is shown in figs. 4, A and 4, D. 

 If a young specimen be compared with an old one it will be 

 seen that in the former case the sheath completely invests 

 the enclosed rods and is equally wide at base and apex (figs. 

 4,B and 4,C),but that in the latter case the sheath, now some- 

 what hardened, has burst at the top and shows much wider 

 at the apex than at the base (fig. 4, A). A young Crenothrix 

 plant is shown in Plate IV. The bursting of the sheath at 

 the apex enables the rods or cocci, as the case may be, to gain 

 access to the outer world, and when liberated they elongate 

 and in their turn form new threads. 



With regard to the dimensions of this organism, the rods 

 vary in length from 2 y, to 7 n or 8 /i. The cocci measure from 

 2 fi to 4 fju in diameter. The sheath closely invests the contained 

 rods, and whilst measuring 2/x to 4 /j, at the base may attain 

 five or six times this width at the apex in a mature specimen. 

 In normal times the rods or cocci are gently thrust out through 

 the apex of the sheath, but when, as stated above, inordinate 

 multiplication takes place, the individuals appear to be gal- 

 vanised into leading a very strenuous life. The whole contents 

 of the sheath break up into cocci, with the result that each 



