November 24, 1904J 



NATURE 



n 



LETTERS TO THE EDITOR. 



\The Editor does not bold himself responsible for opinions 

 expressed by his correspondents. Neither can he jindertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



On the Origin of Flagellate Monads and of Fungus- 

 germs from Minute Masses of Zoogloea. 



Bacterial scums are exceedingly common in ditches and 

 ponds, nature's laboratories, and it is a matter of much 

 importance to know what goes on therein. Some light may 

 be thrown upon this subject by making infusions or macer- 

 ations from cut fragments of various plants, and then ex- 

 amining, at different periods, the scum or pellicle that 

 forms on such fluids. What I have now to say will refer 

 almost e.xclusively to infusions made from hay. The hay 

 employed may be either fresh or old, but it does not do to 

 substitute for hay mere unripe grasses. I have elsewhere 

 shown how remarkably different are the products derivable 

 from living unripe grasses and from ordinary hay.' 



In making such an infusion I have been accustomed to 

 cut the hay into short pieces, to place these in a little beaker, 

 and then to add water so as well to cover the fragments. 

 .\fter maceration for three or four hours at a temperature 

 of about 86° F. (30° C), the infusion has been filtered 

 through two or three layers of the finest Swedish filtering 

 paper into another small beaker. In this way all but the 

 smallest particles, 1/12,000 of an inch or thereabout, will 

 be excluded. For observation of the changes now to be 

 described it is best that the bacterial scum, which soon forms 

 on the surface of the fluid, should be very thin, therefore 

 the depth of the fluid ought not to be more than about one 

 and a half inches — though if one is seeking to make out 

 the origin of ciliated Infusoria infusions of greater depth 

 should be employed in order that a fairly thick pellicle may 

 form. 



When such an infusion is kept under a bell-jar (to exclude 

 dust) at a temperature of about 65° F. (18° C), the pale 

 sherry-coloured fluid in less than twenty-four hours becomes 

 lighter in colour and very turbid. Soon a scum, almost in- 

 visible, begins to form on the surface, composed of several 

 different kinds of bacteria, and in about thirty-six hours 

 small Zoogloea masses of the most varied sizes and shapes 

 begin to appear therein. In Fig. i, A, a portion of such 

 a scum is shown as it appeared at the end of the third day 

 on a hay infusion in which the masses of Zoogkea were 

 exceptionally numerous. The portion of this scum here 

 represented had been transferred on the tip of a sterilised 

 scalpel to a drop of a dilute solution of eosin, which stained 

 the surrounding bacteria a pale red tint, but left the 

 Zoogloea masses unstained, so that they were rendered very 

 distinct. Had logwood been used the results would have 

 been reversed — that is, the Zoogloea areas would have been 

 ■ more or less deeply stained, while the surrounding bacteria 

 would Jiave remained unstained. 



Examination of one of these masses with a high power 

 will show its constitution, and reveal the fact that we have 

 to do with an aggregation of separate bacteria imbedded 

 in a jelly-like material. This may be seen from Fig. i, B, 

 which shows a highly magnified portion of one of the 

 Zoogloea masses from the same pellicle after it had been 

 immersed in a drop of a weak solution of Ehrlich's eosino- 

 phyle fluid, which stained the surrounding bacteria a 

 yellow tint, while it left the Zoogloea mass unstained. The 

 slightly altered bacteria within the Zoogloea mass are at 

 this early stage plainly to be seen, though later on they 

 become more or less obscured by reason of progressive 

 molecular changes taking place in the mass during its 

 subsequent transformation. 



Some of these Zoogloea masses are destined ultimately 

 to be converted into numbers of flagellate Monads or of 

 .\mceb;e, while others become resolved into heaps of Fungus- 

 germs. I have found it impossible to tell from the mere 

 microscopical appearance of the Zooglcea masses whether 

 they are destined ultimately to yield Monads or Fungus- 

 germs. The latter transformation is undoubtedly by far 

 the commoner of the two, and when I was working for 

 many months at this subject during 1899 I was unable to 

 1 "Studies in Helerogenesis," p. 87 (1904). 



NO. 1830, vol.. 71] 



find any good specimens, capable of being photographed, 

 showing the conversion of Zoogloea masses into Monads, 

 although I many times saw and photographed Monads 

 originating from the pellicle as discrete motionless cor- 

 puscles — especially when the infusions were kept at a 

 temperature of about 72° F. (22° C.).' But one day last 

 month, on October 19, desiring to make certain observ- 

 ations, I made a weak infusion from a portion of a small 

 handful of hay gathered in Norway more than two months- 

 previously, which had since been kept in a small cardboard 

 box. The infusion was prepared and filtered in the manner 

 already indicated, and divided into two portions : one, which 

 we may name A, being placed in a small open beaker and 

 left bfeneath a bell-jar at the end of the mantelpiece in my 

 study ; while the other (a very small portion), which we 

 may name B, was put into a* small half-ounce earthenware 

 pot, over which the cover was placed. The two specimens 

 of the infusion, covered and uncovered, were then left side 

 by side beneath the bell-jar, so that the temperature to 

 which they were exposed might be as nearly as possible 

 similar. Some of the changes in the scums that formed oni 

 the surface of these fluids are now to be described. 



Origin of Flagellate Monads from Minute Masses of 



Zoogloea. 



.\. When examined fifty-one hours after the time of 



filtration the scum on this infusion was found to be very 



thickly crowded with small masses of Zoogloea varying 



much in shape and actual si^e, as shown in Fig. i, .\. 



Fir,. I.— A, Zooglcea n 

 A portion of one of the 



1 the scum on a hay infusion (x 100) ; B 

 s showing the contained bacteria ( x 50c). 



In the course of the fourth day very many of the smallest 

 masses were seen to be undergoing segmentation into small 

 motionless spherical bodies, while multitudes of active 

 flagellate Monads of the same size were for the first time 

 seen in the fluid and in the midst of the portion of the scum 

 under examination. When a similar examination had been 

 made twelve hours previously not a single Monad was seen ; 

 now there were swarms of them, and all were of about the 

 same size. 



In Fig. 2, A (xsoo), some of these small masses are 

 shown together with their contained bacteria; B (X375> 

 shows a number of the small masses undergoing segment- 

 ation ; while C (X700) shows one of these bodies more 

 highly magnified, in which the segmentation into embryo 

 Monads, still in a motionless condition, is almost complete. 



In the course of the next day the Monads were found 

 in prodigious numbers. They were spherical or ovoidal in 

 shape, and provided with a single flagellum about twice 

 the length of the body. Under a high power a nucleus 

 could be distinctly seen, generally surrounded by a circle 

 of very minute granules. In addition, two or three larger 

 granules were to be seen— one of them, larger and more 

 iiighly refractive than the others, being often present m the 

 1 " Studies in Helerogenesis," pp. 69-73, Figs. 53-55- 



