446 PEOE. A. DENDY Olf PONTOBOLBOS, 



should be compared with fig. 7, showing a portion of one of the 

 deeper layers where all the rods have disappeared and the- 

 empty sheaths are brought into view by the chlor-zinc-iodide 

 method. 



It appears to me that there are two possible views as to the- 

 nature of Fontoholhos : first, that the organism is entirely 

 bacterial in origin, the flocculent layers and network being due- 

 to the formation of slime or jelly by the bacteria themselves ; 

 second, that it is due to symbiosis between the bacteria and 

 some gigantic rhizopod the protoplasm of which is seen in the- 

 flocculent layers and network. We may consider these two 

 views separately. 



That the great bulk of the entire organism consists of 

 filaments of some Schizophyte and their sheaths, I think has 

 been already sufficiently demonstrated. The filaments appear to- 

 be very closely related to Crenothrix. Crenothrix Kuhniana is 

 described as consisting of " cocci, rods and thread-forms. The 

 threads are colourless, l*5-5 jjl thick, and club-shaped at the 

 extremity, reaching a diam. of 6-9 jjl. The threads form colonies 

 with a brick-red, olive-green, or dark-brown to brown-black 

 coloration, caused by impregnation with oxide of iron. The 

 threads are distinctly articulated, and ensheathed. The segments 

 are set free when the sheath bursts, and develop into new 

 threads. In other cases the segments remain enclosed, and 

 subdivide into discs, which, by vertical fission, break up into 

 globular forms (cocci). These again develop into new threads, 

 either within the sheath, eventually penetrating it, or after they 

 are set free." 



" The micro-organism appears in little whitish or brownish 

 tufts in wells and drain-pipes, and it not only renders drinking- 

 water foul, but may stop up the narrower pipes." 



The above description is taken from Crookshank's 'Manual 

 of Bacteriology ' (2nd edition, p. 322). The figures showing 

 colonies of threads growing out of a zoogloea of cocci are 

 especially suggestive of a comparison with Pontoholhos. The 

 chief differences appear to be that in JPontoholbos the threads 

 are more slender and of the same diameter throughout, and that 

 they grow much more closely together to form compact layers 

 on the top of which the zoogloea is presumably passed out 

 from the upper ends of the sheaths. This zoogloea, if such 

 it be, may form the base from which another layer of rods grows 



