December 24, iqh] 



NATURE 



463 



1 I K., r, r.rf>inrp(l at q8° F.. and the scum on which sub- 



formalin is run in, and t..^ --■-. j, .V-^KottAr 



But where there are bro^^n ^ ""g^^-g^""")? ^^*",^f, ^' 

 to let the specimen remain in water, as the formaUn, 

 and also glycerin, would speedily remove their char- 

 acteristic colour. ^ , J 11 V.^o-lrpn<; 



When some of these first-formed small Zoogloeas 

 are examined with a high power, it becomes obN^ous 

 that thev are simple aggregates of bacteria, such as 

 mav be seen in Figs. 2, A, and 3. Further, just the 

 same kind of bacteria are to be seen within them as 

 in the scum immediately around; and the bacteria 

 from the scum of the infusion prepared at 90 i'- do 

 not differ morphologically from those of the scum on 

 the infusion prepared at 98° F. , . ,, j-fr^^^nt 



It must come to be a question whether the different 

 products ultimately yielded by the two sets o 

 Zoogloeas can in- part be attributed a) to the fact that 

 the constituent bacteria are actually differ^"* in the 

 two cases, or (b) to the fact that the shghtlv different 

 (and far from lethal) temperatures at which the tv^o 

 infusions have been prepared, have ^^^-^^d to modif) 

 the phvsiological attributes of the same set of bac 

 teria The latter seems to me to be b> far the 

 more probable explanation, looking in Pf rt to the 

 .eeming morphological identity, and also to the possi- 



sequentlv vielded only Fungus-germs. 



Fitr 2 A shows a portion of one of the Zoogloeas 

 It an early 'stage, in which the bacteria are still very 



Fig. 2.— X500. 



distinct, though later they often tend to become more 

 or less enlarged and altered in appearance. In 

 Fic' 2 B a later stage is shown in which much seg- 

 me^ntation has taken place, where the bacteria are no 

 lonc^er recognisable, and the segments have assumed 

 the glistening appearance already referred to 



Fig. I. — X2C10. 



bilitv that the exposure to the higher temperature 

 of 98° F. for three hours mav have somewhat de- 

 c^raded the molecular structure of the bacteria, so that 

 These particular aggregates are only eventually capable 

 of vielding vegetal rather than animal products, and 

 that too, after rather more than twice as long a 

 period. Important facts in support of this conclusion 

 will be reported later on. 



It is moreover, a verv remarkable circumstance that 

 almost until the ultimate products of segmentation are 

 reached there seems to be no means of distinguishing 

 bv mere microscopical examination whether the 

 Zoo£jloeal masses are going to yield brown Fungus- 

 germs, Monads, or Amoebae. As they grow and 

 develop, thev all tend to segment into smaller and 

 smaller portions; and after a time the constituent 

 bacteria become hidden owing to molecular changes 

 in the c*loeal material. These are also shown by the 

 segments becoming glistening and more refractive 

 and at the same time more receptive of logwood and 

 other stains. 



Conversion of Uhmiaie Segments of Zoogloeas into 

 Brown Fungus-Germs. 

 In Figs. 2-5 are to be seen portions of some of the 

 Zoogloeas from pots containing an infusion that had 



NO. 2^S6, VOL. 94] 



Fig. 3. — X500. 



The date at which the change into brown Fungus- 

 <rerms begins is subject to considerable variation, but 

 'this colour is rarelv seen before the eighth or after 

 the thirteenth dav— the time needed being in part 



