280 Profs. Percy Frankland and Marshall Ward. 



very slow and very slight movements, due to almost imperceptible 

 curvatures of the filament. These can be traced by watching the 

 growth for a few minutes under the eye-piece micrometer, and are 

 interesting as indications of slight movements of nutation. As I 

 shall have to speak of these, and the measurements I have made of 

 them and of the rate of growth, when describing the behaviour of the 

 older filaments, however, they may be passed over here simply with 

 the remark that they do occur. 



Even at this early stage, or a little later, the filaments, especially 

 in broth cultures, may begin to break across, generally, but not 

 always, at the oldest septum (figs. 11 e, and 10 /), though this process 

 is by no means the common or normal one in rapidly growing 

 cultures (fig. /). 



Sooner or later, however, some amount of fission does occur, and 

 the further behaviour of the two or more broken filaments is 

 interesting, as throwing light on the formation of the tresses and 

 strands, and their false branches, which we meet with later. 



Fig. 11 /and g is an instructive case in point. As the first stage 

 shows, the filament broke at the oldest septum when little more than 

 eight times as long as the spore, and consisting of four segments, 

 and when only ten hours old. The lowermost two-celled segment, 

 proximal to the spore, then slipped its now rounded tip to the right, and 

 continued growing ; the uppermost, free and distal, two-celled seg- 

 ment also grew so that both ends travelled further apart, and in such 

 a way that the tip of the proximal segment slipped along its right 

 side. Further divisions followed on growth in both cases, and the 

 right hand (proximal) segment again broke during the night at its 

 oldest segment, when it had divided into four cells, the ends again 

 slipping over one another, so that at nine o'clock next morning 

 (twelve hours later) the state of affairs was as in fig. 11 g. This was 

 a gelatine culture, not growing very rapidly, but I shall have to 

 revert to these phenomena later in discussing the process of growth 

 in broth cultures. 



It is already intelligible, however, that this slipping of the broken 

 filaments one over the other, each portion growing independently 

 soon gives rise to strands or tresses compounded of numerous 

 filaments, the free ends of which stand off as false branches (the 

 same thing is beginning in fig. 10 / and gr), and so the initiation of a 

 colony, with offshoots radiating in all directions into the surrounding 

 medium, is established. 



From the fact that well isolated spores, freely suspended in a drop 

 of broth, give rise to filaments which may grow to many hundred 

 times the length of the spore before any breaking across occurs, and 

 that such breakage is very apt to occur when one such long filament 

 eventually abuts on another, or on some obstacle which bends the 



