288 



INTRODUCTION 



[Cn. X 



are summarized in the curve, Fig. 79. This shows how the 

 growth in length of the bacterial rods is delayed at intervals 



70 fJ. 



60 [l 



10 [J. 



30 ft 



20 \l 



FIG. 79. Curve of growth of a bit of a filament of Bacillus ramosus, 27.30 M long at 

 the beginning and 70.88 /* at the end of the period of observation. The curve 

 shows certain periods of diminished growth (indicated by the arrows below the 

 curve), which correspond to cell-division. From WARD ('95, p. 300). 



by the nuclear divisions and the accompanying formation of 



transverse septa.* 



The course of 

 normal growth may 

 now be studied 



111 



10 



FIG. 80. Curve of length of shell of Lymnaea stagnalis 

 at intervals from hatching up to 85 days. From 

 SEMPER, Animal Life, p. 163. 



* Attention niay here 

 be called to a phenomenon 

 which has repeatedly 

 been observed when a 

 single growing mammal 

 has been weighed at 

 regular intervals. This is 

 a sort of alternation of 

 periods of unusually rapid 

 growth with periods of 

 diminished growth, the 

 interval being a day or 

 two. There is an irregu- 

 larity in the length of 

 these periods. See SAINT- 

 LOUP, '93 ; compare also 

 MINOT, '91, Table XIV. 



