186 HETEROGENETIO CHANGES IN 



growth, the individualisation, and the processes of segmentation 

 taking place in these minute masses of Zoogloea. We have also to 

 do (2) with the question of the ultimate destination, or the trans- 

 formation, of the products of such segmentation. These are two 

 parts of the subject that are to some extent distinct, and which are 

 well worthy of separate consideration. 



(i) The Developmental Tendencies in Zooglcea. If it be asked 

 what amount of knowledge bacteriologists possess on this subject, 

 the answer must be "extremely little," if we are to judge from 

 the paucity of information on the subject which is to be found in 

 any of their text-books. Yet if they would only deign to look at 

 what takes place in the scum on a filtered hay-infusion, they could 

 very soon satisfy themselves that Zoogloea masses not only grow 

 rapidly, but undergo definite developmental processes, associated 

 with marked molecular changes — as evidenced by their different 

 behaviour at different stages to logwood or other stains, as well as 

 by the results of microscopical examination. And, while these 

 molecular changes are taking place, the masses may segment into 

 larger or smaller portions and often into minute spherical or ovoid 

 units, showing that an organising process is taking place — as may 

 be seen in Figs. 16-20, and in others. 



If we look at the constitution of Zoogloea masses, as shown in 

 Figs. 12 and 21, A, it may be seen that we have only to do with 

 Bacteria imbedded in a varying proportion of gloeal material. But 

 later on, when the mass has grown, and some amount of segmenta- 

 tion has taken place, as in Fig. 11, A, it may often be seen that we 

 have still only to do with aggregates of Bacteria. At other times, 

 it is true, the molecular changes that have taken place in the mass 

 have so altered its constitution (making the segments very refrac- 

 tive) that the included Bacteria are no longer recognisable, as in 

 Figs. 19 and in 21 C. 



But now an important link in the proof of my views may be 

 mentioned. The Zoogloea masses in their early stages are colour- 

 less, but a large proportion of them are, as I maintain, ultimately 

 destined to give rise to brown Fungus-germs. The assumption of 

 the brown colour may, however, be taken on by the segments of 

 the Zoogloea while they are still only aggregates of Bacteria, as 

 may be seen by Fig. 11, A (X500), showing nearly spherical seg- 

 ments of a large Zoogloea mass which at the time they were 

 photographed were in different shades of brown, and in some of 



