THE PHYSIOLOGY OF CELL-DIVISION 703 
eggs thus treated were left in sea-water without further treatment ; 
a second part after a brief interval were transferred to hypertonic 
sea-water for thirty minutes, and then returned to sea-water; a 
third part were left for varying periods in sea-water containing 
stro KCN. 
TABLE 1 
July 6, 1910. Unfertilized eggs of Arbacia punctulata were divided into four equal 
lots in finger bowls, the sea-water was removed as far as possible, and solutions A, 
A(+Ca), B, B (+Ca) added respectively to each lot. After five minutes the eggs 
were returned to sea-water. Part 1 remained in sea-water, Part 2 were transferred 
after several minutes to hypertonic sea-water (250 cc. sea-water plus 25 cc. 2.5 M 
NaCl); and Part 3 were transferred after about ten minutes into sea-water contain- 
ing KCN to ,“\5 concentration, from which they were returned to sea-water after 
varying intervals. The results were as follows: 
A. Eggs in 250 cc. 0.55 Mm Nal for 5 minutes; thence transferred to sea-water. 
Further treatment as follows: 
1. Eggs left in sea-water. Almost all form membranes and undergo form- 
change or irregular cleavage. Next day the great majority are dead, coagulated, 
and depigmented. A few blastulae—two or three—found in several hundred eggs. 
2. Eggs left in sea-water 5 minutes; thence transferred to hypertonic sea-water 
for 30 minutes; returned to sea-water. A large proportion of eggs form active blas- 
tulae (ca. 50 per cent). 
3. Eggs left in sea-water 11 minutes; thence to ,“., KCN in sea-water; portions 
returned to sea-water after following intervals. 
a. 2 hours. A small proportion form blastulae. Decided increase over 1. 
b. 3 hours. A fair proportion of blastulae, more than in 3a though few com- 
pared with 2. 
c. 43 hours. Like 3b: a fair proportion of larvae. 
A(+Ca.) Eggs left for 5 minutes in 250 cc. 0.55 m Nal plus 15 ec. ¥ Ca Cle; 
thence to sea-water. Part left in sea-water, part treated with hypertonic sea- 
water. 
1. Eggs left in sea-water. Marked contrast to Al. Almost all eggs remain 
round, uncleaved, and unaltered. A small proportion undergo irregular change 
of form and break down. No larve. 
Next day, after 22 hours, the eggs were fertilized with spermatozoa; practically 
all developed into swimming larvae. 
2. Hggs left in sea-water 7 minutes; thence to hypertonic sea-water for 30 minutes; 
returned to sea-water. The great majority of eggs remain unaltered. A small 
proportion are broken down next day and a few feeble blastulae are present. 
On fertilization next day (after 22 hours) most eggs form larvae, but a smaller 
proportion than in Lot 1 swim at the surface of the water. 
B. Eggsin0.55m KCNS for 5 minutes; thence to sea-water. Three lots treated 
as follows: 
1. Egg left in sea-water. Almost all form membranes and undergo change 
of form or irregular cleavage. Next day almost all are dead, coagulated, and 
depigmented. A few blastulae; two or three found in several hundred eggs. 
