350 



Dr. D. Ellis. 



[May 17, 



permanently open. This pressure also causes the side-slipping of individual 

 cells before the sheath hardens, resulting, if the water be moving very 

 slowly, in the cell growing into a " false branch." 



Cell-division takes place at first uniformly throughout the thread, but, 

 after the apex has been opened, it is mostly confined to the basal part, as at 

 the apex only full-developed mature cells can be observed. 



Multiplication. — This is essentially of one kind, viz., by the rejuvenescence 

 of a single cell or a group of cells. The following varieties of this mode of 

 multiplication may be distinguished : — 



1. Multiplication by Liberation of Thread-fragments. — This is the mode 

 followed by motile threads, in which I have seen no trace of a ruptured 

 sheath nor of the liberation of single cells. Some of these motile threads 

 may reach to a length of yu., and even in these the sheath is soft, and 

 envelops the cells very closely. The liberation of thread-fragments has been 

 observed by Zopf in the case of attached threads, and I am able to confirm 

 his statements. In my observations, however, the liberated fragments 

 assumed a spiral form. I propose dealing more fully with this in a later 

 section. 



2. Multiplication by the Liberation of Rejuvenated Single Cells. — On the 

 nature of this mode of multiplication all observers are agreed. Sooner or 

 later, in attached threads, the apex of the sheath bursts, and single cells are 

 pushed out into the surrounding water. These cells are sometimes devoid of 

 motility and drift placidly away, at other times they develop organs of 

 motion, by the aid of which they swim out of the sheath. I have observed 

 the actual liberation of a non-motile cell. It seemed to be thrust out of the 

 sheath by the aid of a small push from behind (fig. 18). There is nothing of 

 a sporogenous character about these cells, for they behave in precisely the 

 same way, as regards growth, division, etc., whether within or without the 

 sheath. They are vegetative cells of the same nature as those of the genus 

 Bacillus. Hoeflich follows this line of thought so far as the non-motile cells 

 are concerned, but he refers to the same when motile as " spores," because, 

 previous to ejection, in addition to the development of cilia, certain changes 

 in vacuolisation occur. The changes which he describes seem to me to be 

 connected with changes incident to the development of cilia. The only 

 difference, therefore, between what is confessedly a vegetative cell and what 

 he calls a " spore " is that the latter is motile. These " spores " appear to 

 me to be merely swarming vegetative cells. Hoeflich does, indeed, refer to 

 the germination of these bodies, but, considering the importance of the 

 point, a bare mention of the fact, and a very inconclusive drawing, are not 

 sufficient evidence to warrant full acceptance without confirmation. 



