194 METEROGENETIC CHANGES IN 



These facts and considerations alone, as I have said, seemed to 

 indicate very forcibly that the corpuscles were formed from the 

 very substance of the pellicle, and that they had not sprung up 

 from multitudes of invisible germs, gradually growing till their 

 full size had been attained, and then multiplying with great 

 rapidity. 



After a time, however, I thoroughly satisfied myself that the 

 corpuscles are, as a matter of fact, only individualised portions of 

 the general Zoogloea mass of which the pellicle is composed — each 

 corpuscle containing several Bacteria. And often when the 

 corpuscles separate, and first begin to exhibit slow oscillating 

 movements, they may be seen to have an exactly similar composi- 

 tion. They appear then as small pellucid spheres, having a single 

 flagellum, and containing in their interior four or five Bacteria, 

 exactly like those in the region of the pellicle from which they 

 have been derived.' These Monads soon increase somewhat in 

 size and become more active ; the Bacteria in their interior are no 

 longer distinguishable and a distinct nucleus is formed, as in 

 Fig. 24, E. 



In some pellicles the discrete corpuscles that are produced in 

 the manner indicated develop into Amoebje rather than into 

 Monads. This probably depends upon some differences, of an 

 unknown nature, in the chemical constituents of the infusion itself 

 favourable to the production of this phase of the Monad-Amoeba 

 couple. That the two forms are rapidly and easily convertible, the 

 one into the other, is very generally admitted. In an infusion 

 made from a bunch of Melica nutans in full flower, minute Amcebse 

 were produced in myriads from the pellicles in this way. Fig. 26, 

 A ( X 375) shows a number of these Amoebae varying much in size, 

 which were found in the pellicle on this infusion. Again, in an 

 infusion made from mixed grasses in full flower (largely composed 

 of Lolium perenne) a thin pellicle was observed, the weather being 

 warm, in which Monads were scarce, but vast numbers of small 

 active Amoebze existed as early as the second day. In regard to 

 the appearance of this pellicle on the fifth day my note-book 

 says : " Three-fourths of the pellicle is now apparently con- 

 verted into AmoebJE, which exist in myriads. Not a single 



' Sometimes, however, the Bacteria are not so clearly recognisable, and 

 the corpuscle as a whole is much more refractive. Similar differences exist 

 also, as I have shown, in regard to the segments into which embryonal areas 

 divide. 



