128 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
If we compare these results with those obtained in chapter 
x1, we find that 50 c.c. of m/2 NaCl+5c.c. of 24 m NaCi 
produce the same effect as 50 c.c. of sea-water+4 c.c. of 
2; m NaCl; in other words, that a mixture of 50 c.c. of } m 
NaCl+1 ¢.c. of 25 m NaCl is about isotonic with sea-water. 
TABLE XIV 
PreRcENTAGE OF EaGs THat? 
DEVELOPED INTO LARVAE 
" “am i) 
CoMPOSITION OF THE SOLUTION AFTER AN EXPOSURE OF 
| 
55 min. | 90 min. | 120 min. 
50 ¢.c. 4 m NaCl+ 3.c.c. 24 m NaCl....... 0 0 0 
50 c.c. } m NaCl+ 4ce.c. 24 m NaCl.. 0 0 0 
50 c.c. 4 m NaCl+ 5c.c. 23m NaCl.. 0 0 1 
50 c.c. } m NaCl+ 6c.c. 23 m Na€l....... 0 1 5 
50 c.c. 4m NaCl+ 7 c.c. 24 m NaCl....... 2 59 70 
50 c.c. + m NaCl+ 8ce.c. 24m Na€l....... 30 80 90 
50 c.c. } m NaCl+10 c¢.c. 24 m NaCl....... 80 90 =e 
50 c.c. 4 m NaCl+12 ¢.c. 24 m NaCl....... 80 a 
50 c.c. 4 m NaCl+14 c.c. 24 m NaCl....... 80 
50 c.c. + m NaCl+16 c.c. 24 m NaCl....... 80 
Now whereas a mixture of 50 c¢.c. of sea-water+10 c.c. of 
24 m NaCl injures the eggs so badly in 60 minutes that only a 
small number develop, and a mixture of 50 c.c. of sea-water-+ 
12 c.c. of 25 m NaCl kills practically all eggs with artificial mem- 
branes in 60 minutes, in a mixture of 50 c.c. of 3m NaC!+16c¢.c. 
of 24 m NaCl 80 per cent of the eggs develop after an exposure 
of 55 minutes. The explanation of this paradox lies in the fact 
that the NaCl solution was practically neutrai, while the sea- 
water is slightly alkaline. We shall see in a later chapter that 
the harmful effect of hypertonic solutions upon the egg 1s much 
greater if they are slightly alkaline than when they are neutral; 
slightly acid hypertonic solutions are still less injurious than 
neutral ones, or, in other words, the harmful eifect of hypertonic 
solutions increases, within the limits considered, with the con- 
centration of the hydroxylions. The injurious effect of these 
hypertonic solutions is diminished, if not absent, in a solution 
