98 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
2. We will now inquire how the time which the eggs must 
remain in the hypertonic solution varies with the osmotic pres- 
sure of the latter. 
The eggs of a sea-urchin were treated with sea-water con- 
taining butyric acid, and all formed membranes. The eggs 
were then distributed among solutions consisting of 50 c.c. of 
sea-water+respectively, 0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, and 
14 c.c. of 24 m (grammolecular) NaCl solution. A portion of 
the eggs was transferred from each of these solutions to normal 
sea-water after 33, 45, 57, 68, 98, and 128 minutes, and the 
percentage that developed into larvae determined for each 
portion. Table VII gives the result. The temperature of the 
hypertonic solution was 16° C. 
TABLE VII 
| _ PERCENTAGE OF THE EGGs OF 
S. purpuratus WHIcH DEVELOPED 
INTO LARVAE AFTER REMAINING IN 
NATURE OF THE SOLUTION THE SOLUTION 
l 
33 | 45 | 57 | .68 | 98 | -128 
min. min. | min | min. | min. | min. 
HOC:COl S6a-waber in. sce eee O2F20 0 0 0 0 
50 c.c. of sea-water+ 4¢.c.2}mNaCll 0) 0 0 0 0 | afew 
50 c.c. of sea-water+ 5c.c.24m NaCl] 0} O 0 1 30 60 
50 c.c. of sea-water+ 6c.c.24 1m NaCl} 0 0 2 50 | 100 10 
50 c.c. of sea-water+ 7 c¢.c.24m NaCl) 0 1 30°}. 70 70 0 
50 ¢c.c. of sea-water+ 8 ¢.c.24m NaCl] 0 1| 50 80 |afew| 0O 
50 c.c. of sea-water +10 c.c.24 m NaCl) 0) O 10 10 1 0 
50 c.c. of sea-water+12 c.c. 24 m NaCl) 0 0 | afew 0 0 0 
50 c.c. of sea-water+14c¢.c.2}m NaCl) 0/| O 0 0 0 0 
This brings out two facts. In the first place the effective- 
ness of the hypertonic solution has definite limits. The addi- 
tion of 4 c.c. of 25 m NaCl is too small, the addition of 12 ¢.c. too 
much, and in the latter case the eggs go to pieces by disinte- 
grating into drops. Secondly, we see that when once the opti- 
mum concentration is reached, i.e., that which produces the 
1 Loeb, ‘“‘Ueber den Unterschied zwischen isosmotischen und isotonischen 
Losungen bei der kiinstlichen Parthenogenese,”’ Biochem. Zeitschr., XI, 144, 1908. 
