36 PROFESSOR LA>fKESTER. 



multiplication of units or centres of organization -which is 

 observed in other masses of protoplasm. 



Just as we find exceptional cases in animal and vegetable 

 cells in which a mass of protoplasm gives rise simultaneously 

 to numerous nuclei, each of which becomes surrounded by a 

 segregated mass of protoplasm and produces a numerous 

 cell-progeny by multicentral segregation, so it appears that 

 in the large discoid macroplasts of Bacterium rubescens a 

 formation of innumerable new plastids occur — not by a pro- 

 cess of progressive division into two, four, eight, &c. — 

 but by a simultaneous multicentral segregation. Such 

 appears to me to be the explanation of the minutely granular 

 structure detected only with the highest powers in such 

 specimens as figs. 17, 18, and 21. The granules indicate so 

 many new units or centres of organization, and each of them 

 takes on independent growth, enlarges and finally becomes 

 separated from its fellows by a gelatinous envelope. 



It would be necessary in order to establish this view to 

 watch the steps of the process in one and the same macro- 

 plast ; and it is clear that during the period of increase in 

 the size of the new units, the whole mass must greatly en- 

 large. I have not succeeded in actually watching the process of 

 development which I suppose may take place, but I draw 

 attention to the fact that there is on the whole evidence of a 

 proportionately larger size in those macroplasts which are 

 coarsely as compared with those which are finely granular. 

 This fact does not, however, count for very much, since one 

 observes granular macroplasts of very various sizes from the 

 ao'ooth of an inch upwards. 



A second development of the macroplasts took place in 

 the same jar after an interval of six months, during which 

 time the "growth" had been carefully fed up, and it had 

 become difficult to find any specimens of them still remain- 

 ing. The second development of these bodies occurred after 

 the supply of nutrient matter to the jar had again been dis- 

 continued for some weeks. 



Specimens of the macroplasts in various stages of segrega- 

 tion were mounted in glycerine, where they preserved their 

 colour for a month or so, but subsequently assumed a pale, 

 dirty green tint. Such specimens were sent by me to various 

 naturalists interested in the study of the Bacteria, whilst my 

 friend. Professor Thiselton Dyer, examined the growth in its 

 living condition in my laboratory at Exeter College. 



Supposing the most finely granular macroplasts to be 

 m.echanically broken up into their minute constituent gran- 

 ules, we should have a very prolific source of those execs- 



