78 



NATURE 



[November 24, 1904 



.1 



posterior half of the body of the organism, and there show- 

 ing faint oscillations. Numbers of the Monads that were 

 aggregated between three small contiguous air bubbles are 

 shown in Fig. 2, D (X125), as they appeared under a low 

 power of the microscope. Many of them were in active 



Fig. 2.— a. Small Zoogtea masses from the hay infusion (Xsoo); B, Other 

 of these masses undcrg'-ing segmentation (X575); C, One such mass 

 the seymenialion of which is nearly complete (X700); D, Monads 

 derived from products of segmentation (X125). 



movement and are not shown, but those that were stationary 

 were photographed by a very brief e.xposure. 1 found it 

 impossible to photograph these particular Monads under a 

 high power because they were mi.\ed up with active bacteria, 

 and were themselves very delicate in te.xture. The move- 

 ments of these bacteria could not be arrested except by a 



Flu. 3. — A, Portion of pellicle taken li..iii il,e put ^ -^ 5^ 

 masses about to seg.nent ( X 500) ; C, Small Zooglu 

 undergone complete segmentation ( x 500). 



comparatively strong osmic acid solution, or by exposure 

 to the vapour of a i per cent, solution for more than half 

 a minute, ,md in either case the result was to make the 

 Monads almost invisible, if it did not cause their complete 

 diffluence. 



B. The closed pot was not opened until the end of the 

 fifth day, and I then found the surface of the infusion 

 covered with a very thin, scarcely perceptible film of 

 bacteria, which on microscopical examination was seen to 

 be densely crowded with very ininute Zoogloea masses such 

 as are shown in Fig. 3, A (X500). Not a single Monad 

 was to be seen, but many of the masses were found to be 

 about to segment as in B, or actually segmenting as in C, 

 into a number of motionless spherical corpuscles. 



During six subsequent days I uncovered the pot for a 

 moment to take up on the tip of a sterilised scalpel a portion 

 of the scum for examination, and on each occasion found 

 llie minute Zoogioea masses presenting similar characters, 

 except that day by day a rather larger number of them 

 showed evidences of segmentation, though not a single 

 active .Monad was to be seen. 



The Zoogloea masses formed in the dark, and in a com- 

 paratively airless pot, were not only different in character 

 from those formed in the open vessel, but it would seem that 

 their process of change was slower and was in part arrested 

 by the opening of the pot, since after eleven days there 

 was still not a single active Monad to be seen, though in 

 the open vessel swarms of them were found during the 

 fourth day.' This arrest of the process of change recalls 

 the similar arrest which was always found to occur when 

 the pot was opened in which Hydatina eggs were being 

 transforiTied into ciliated Infusoria of the genus Otostoma.^ 



It so happened that on the very day that I first observed 

 the segmentation of the small Zoogloea masses in A I had 





Fig. 4. — A, Minute Zoogli.ca masses in various stages of change ( X 500) ; 

 B One of these masses in which segmentation has been nearly com- 

 pleted (X700). 



on my work-table under a bell-jar a small petri dish in 

 which a tuft of dead lichen had been soaking for a few 

 days in distilled water. There was a very thin scum here 

 and there on the surface of this water, and on examining 

 a portion of it I was surprised to find that it also was 

 crowded with small Zoogloea masses, many of which were 

 apparently in different stages of segmentation into Monads, 

 though the majority of them showed no signs of segment- 

 ation. Being busy with what seemed at the time to be 

 the more important A infusion, I did not examine this new 

 scum again until after the expiration of two days, and then 

 I found crowds of active NIonads, and all the Zoogloea 

 masses now in different stages of segmentation such as 

 are shown in Fig. 4, A {X500). The only portion of an 

 unaltered mass that I could find is seen on the left hand 

 side of this figure, contiguous to the black speck. In 

 the two days all the small Zoogloea masses had either 



1 Examinations of the scum taken from th* pot have since been made at 

 intervals, during another week and still, up to the eighteenth day. not a 

 single Monad has been met with, though very many of ihe small Zoogloea 

 masses have been found segmenting into pale brown Fungus-aerms. But 

 nine days ago (in order to test the question whether th-^ premaiure opening 

 of the pot had caused an arrest of the formation of Monads) I made another 

 similar infusion from the same hay, and placed some of it in another small 

 half-ounce pot, which was opened for the first lime to-day. In the first 

 portion of the scum obtained from this second pot I found swarms of active 

 Monads, and also heaps nf the small brown Fungu's-germs resulting from the 

 segmentation of other of the Zooglcea masses. — Noi^ember 



'Studit 



I Heterogenesis," pp. 49-51, and xiv. 



NO. 1830. VOL. 71] 



