32 Regulation of Size in Unicellular Organisms 



(Taliaferro, '28), and the duration of the daylight 

 cycle to which the host birds were subjected (Boyd, 



'29). 



Bacillus ramosus. Among bacteria, very careful 

 measurements of growth were made by Marshall 

 Ward ('95) in Bacillus ramosus. This organis m forms 



80 



'0 20 40 60 80 100 120 



Time in minutes 



Figure 16. Growth in length of a chain of Bacillus ramosus in a hanging 

 droo of broth. At each of the arrows which point downward septa be- 

 tween daughter cells first became visible, and growth was evidently pro- 

 ceeding at its maximal rate. At each of the arrows which point upward 

 fission of the cells was occurring, and growth was evidently proceeding 

 at its minimal rate. (Redrawn from Ward, '95, p. 300, with the permission 

 of the Royal Society.) 



chains of rod-like individuals. The thicknesses of the 

 cylinders were said to be uniform, however long the 

 individuals and the chains ; so that growth in volume 

 was proportional to length. Under the conditions of 



