196 HETEEOGENETIC CHANGES IN 



pellicle that I have recently examined, in which such corpuscles 

 were found in enormous numbers, many of them being rather 

 larger than usual. They were first seen when a small pot contain- 

 ing some hay-infusion was opened after four days, during which it 

 had been exposed to a temperature of 70° F. (21° C). The edge 

 of a portion of this pellicle is represented in Fig. 25, A (x 500), 

 while in B (x 700) some of the separate corpuscles are shown 

 more highly magnified, so as to reveal the nature of their contents. 

 Nothing like a nucleus is to be seen, nor can one be detected by 

 the use of any of the ordinary stains, even when the corpuscles 

 have been allowed to soak in them for many hours. Logwood, 

 carbo-fuchsine, gentian violet, and mastzellen stain have all yielded 

 negative results. Not a trace of a nucleus is to be found, and the 

 corpuscles seem to be mere individualised portions of Zoogloea 

 intermediate in size between the brown units on the way to the 

 production of Fungus-germs, which are shown in Fig. 11, E and F, 

 and, like them, containing only a few Bacteria in their interior. I 

 have examined such corpuscles ever and over again, and always 

 with similar results. If they do not speedily develop, a limiting 

 membrane is produced which enables their contents to resist 

 staining for some time, and causes the corpuscles themselves to 

 shrivel if they are mounted in glycerine and water. When, how- 

 ever, these corpuscles develop quickly, which is the rule, they give 

 rise more or less suddenly, as I have said, to swarms either of 

 Monads or of minute Amoebae, and then, when thus developed, a 

 delicate nucleus can generally be recognised even without the aid 

 of stains. 



While the discrete corpuscles that develop into Monads and 

 Amoebae seem almost always to be produced from the under layer 

 of the pellicle, those that develop into Fungus-germs are almost 

 as invariably produced from its superficial layer. The fact of 

 their origin from the substance of the peUicle itself is therefore, as 

 a rule, much more readily to be made out than that of the discrete 

 corpuscles whose origin and nature we have previously been 

 considering. 



The discrete Fungus-germs may easily be observed to commence 

 by the individualisation of small ovoidal or spherical portions of the 

 pellicle, in which, at first, the contained individual Bacteria are 

 distinct, as may be seen in Fig. 27, A ( x 375), which shows the 

 germs as they were originating on the third day on the surface of 

 a hay pellicle ; or in B, on the fifth day, from a pellicle on an infusion 



