1905.] Effects of Alkalies, etc., on Eggs of Echinus. 125 



Summary of Results on Rapidity of Growth. 



The following conclusions may be drawn from the observations on the 

 developing eggs in the living condition recorded in Tables I to XI, which 

 are also illustrated by figs. 1 to 17, drawn from sections of the eggs developed 

 in the experiment described in Table XI. The sections were drawn under a 

 low magnification (61 diam.) with the Zeiss Zeichen-ocular. The eggs 

 shown in the drawings had all developed, for the same period (8 hours) in 

 the different media specified, from the same brood of eggs, and the eggs were 

 subsequently fixed and stained as described above. 



1. The extreme limits of variation of hydrogen and hydroxyl ion within 

 which growth is possible are very narrow. Addition of 0*0015 M. of caustic 

 alkali (see figs. 3 and 7) on the one hand or of O'OOl M. of acid (see fig. 4) 

 practically stopping all cell-division. 



2. A slight increase in alkalinity favours growth and cell-division and at 

 the same time tends to produce irregularity in size and shape of the 

 resulting cells (contrast fig. 1 with figs. 2, 6, 8, 9, 10, 11, 12, 15, 16, 18). 



3. In the case of small additions of acids no such favouring action is 

 observable, but from the beginning cell-division and growth are inhibited 

 (see Tables). 



4. Increase in alkali above the optimum amount leads to increased and 

 irregular nuclear division unaccompanied by complete cell-division. As a 

 result the cells become multi-nucleated. The cells also become excessively 

 irregular in size and shape (see figs. 3, 7, 8, 10, 15, 16, 17, 18). 



5. On the other hand increased acidity leads in many cases to action upon 

 the chromatin of the nuclei, so that in the sections the nuclei stain faintly 

 and are comparatively few in number, and there is no proliferation of nuclei 

 in the undivided cells, similar to that seen in the case of alkali (sec figs. 4, 5, 

 13, 14). 



6. The primary factors affecting the rate of growth appear to be the 

 variations in concentration of hydroxyl and hydrogen ions. Thus all 

 the caustic alkalies are of approximately equal power and there is little 

 or no action of the Kation (see Tables and contrast figs. 2 and 3 with 

 figs. 6 and 7). But in the case of the phosphates of the alkalies where the 

 hydrogen and hydroxyl ion concentrations are comparatively low, there 

 appears in addition to be a specific factor. See the marked action of 

 0-0025 M. 2NTaH 2 P0 4 in practically stopping cell division, while 0-0050 M. of 

 Na 2 HP0 4 has a favouring action (contrast figs. 13 and 14 with figs. 15, 

 16, 17). 



