198 Transactions of the Society. 



It was not until three years ago that a clear indication on this 

 subject arose, and close observation has since completely established 

 it. It will be remembered that each of these forms terminates a 

 long series of fissions in what is practically a genetic fusion. The 

 two last of a long chain of self-divided forms fuse into one, become 

 quite still, and at length the investing sac bursts, and a countless 

 host of germs are poured forth. Figs. 5-8, on plate VII., show 

 the sacs of each of the four forms chosen, in the act of emitting 

 germs. 



Now the study of the behaviour of the minute bodies thus 

 emitted was from one aspect by no means difl&cult, for they were in- 

 active, and minute as they are, they are amenable to all our highest 

 power lenses. But the only observation our most patient work could 

 effect upon them, was as our papers show, simply growth — gradual 

 enlargement — the ultimate, but as to time, uncertain appearance of 

 the nucleus — the somewhat saltative appearance, of the flagella — 

 and the attainment of the adult size and condition. 



It was noticed in every case that the germs when first thrown 

 from the sac were semi-opaque. Light was transmitted but feebly, 

 if at all, through them. But in from fifteen to thirty minutes they 

 had become clearly hyaline and strongly refractive : at the same 

 time they had grown most sensibly larger. One thing impressed 

 us from our earliest observations on the growth of these germs, and 

 it was that when the minute hyaline globule had grown to from 

 the tenth to the eighth of the long diameter of the adult, there was 

 a distinct pause, an apparent arrest of growth, suggesting in our 

 earlier observations the death of the organism. This lasted some- 

 times forty or even fifty minutes. I am now able to fully interpret 

 this. It is the nucleus, that grows to its limit of size, and the 

 pause in outward action is employed in the internal development of 

 the nuclear structure. 



For illustration here I select one of the larger of the true septic 

 organisms. It is figured by Ehrenberg, and known as Polytoma 

 uvella, and is seen in plate VII. fig. 2. It is on an average the 

 1/1200 of an inch in length, and its germ and nucleus are rela- 

 tively large. The germ grows to about the 1/5500 of an inch in 

 long diameter in the course of three hours, becoming a beautiful 

 long oval, with no discoverable structure, plate VIII. fig. 1. But 

 at this point there is a distinct arrest in the outer growth, and 

 it lasts from forty to fifty minutes. 



It has been impossible, hitherto, to determine whether or not 

 at this stage there is an investing wall to this hyaline globule : and 

 by optical methods alone it is difficult at any stage to fully de- 

 termine it. But by a one-and-a-half per cent, of acetic acid, to 

 which varying quantities of methyl-green are added, it is clearly 

 developed, by being run carefully in upon the living organism ; or 



