288 



INTRODUCTION 



[CH. X 



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

 growth in length of the bacterial rods is delayed at intervals 



70 /n 



60 /J. 



60 /Li 



30 // 



20 fJL 



PFR.n o NM GROWTH 8 ECONO PERI OF MINMrGROWTH.S a 3 

 PERIOD OF MINM. GROWTH, WHEN ZD CELL DIVISION 



A WHEJI FIRST CELL DIVISION OCCURRED. 



OCCURRED. 



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

 the beginning and 70.88 A* 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 



20 



MM. 



10 

 MM. 



L 



in 



20 



40 



100 



CO 80 



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

 at intervals from hatching up to 85 days. From 

 SEMPER, Animal Life, p. 163. 



* Attention may 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- 

 LOU P, '03 ; compare also 

 MINOT, '91, Table XIV. 



