304 Profs. Percy Frankland and Marshall Ward. 



moiety measuring 31 '85 fi. Each of these portions was again sub- 

 divided by a septum ; the distal one, by a septum B, into a distal 

 moiety just over 17 fi in length, and a proximal moiety not quite 13 yu 

 long ; the proximal one, by a septum B', into a distal moiety measuring 

 just over 17 /*, and a proximal moiety slightly more than 15'5 fi. 

 Close observation showed that each of these was again sub-divided by 

 a faint, approximately median septum, into two cells. 



FIG. 28. 



i i Total 62 MI 



Now it is perfectly obvious from this that the various subsidiary 

 segments or cells, measured at any period, are not of exactly the same 

 length. 4 



At 12.27 I again measured, as exactly as possible, the relative 

 positions on the scale of the above septa to see if I could determine 

 the relative rates of growth of the various segments in the intervening 

 twenty minutes. 



The septum A had moved backwards nearly 3 /u. on the scale, and 

 the apex and base of the whole segment were driven apart about this 

 distance. This suggests that the growth (intercalary) had occurred 

 chiefly in the distal part of the original segment, and such was the 

 case. 



The distance between the septum B and the apex was not 

 measurably altered, i.e., the part to the distal side still measured 

 17'29 fi ; but the distance between B and A had increased from 

 ] 2'74 to 1 6'38 fi. On the proximal side of the septum A no appreciable 

 changes had occurred. It is true, my measurements, as multiplied 

 out, are a trifle different from those first made, but the differences 

 may be neglected, as of course I could not measure to the decimals 

 concerned. 



What does come out, and very clearly, is that during the interval 

 named the growth was entirely in one only of the four cells, and not 

 in all of them. It is obvious that such phenomena complicate the 

 question of the growth of the entire filament still more, and no doubt 

 some of the minute variations observed are due to such events as 

 these. 



I made the following measurements under the 1 /20th immersion, on 

 a terminal segment 36 /t long, in the sister culture to the last one, 



