•^34 CRESSWELL SHEARER AND DOROTHY JORDAN LLOY^D. 
passed tlirongli liyper-alkaline and hypertonic sea-water to 
normal sea-water. The degrees of segmentation at varying 
times in the but 3 ’ric solution, other factors being kept con- 
stant, confirm tlie idea that times longer than about T5 
minutes cause some damage to the eggs. Table II gives one 
series of our experimental numbers. The eggs after butyric 
acid treatment were washed thoroughlj^ and transferred to — 
(1) 2 c.c. X/10 NaOH -j- 50 c.c. sea-water for 7 minutes. 
(2) 8 c.c. 2’5 M NaCl -f 50 c.c. sea-water for 8 hours. 
(3) Normal sea-water. 
Note. — In (3) the low percentage of hlastnlaj may possibly be due to 
the eggs having only received one washing in sea-water after the 
liutyric acid. 
'J’lie alkaline sea-water into which the eggs were placed 
after membrane formation was tried in various strengths and 
for different times. The time factor did not seem to be of 
much importance within fairly wide limits (4-10 minutes), and 
as success in obtaining blastulfe is largely dependent on the 
rapidity of working, we ultimately adopted six minutes as a 
uniformly convenient time for exposing the eggs to its action. 
The strength of N/10 NaOH which gave us the best results 
for the seasons 1911 and 1912 was "2 c.c. in 50 c.c. of sea- 
water, but probably this factor Avill be found to vary from 
3 "ear to A^ear. Table III gives some of our experimental 
numbers. 
The eggs considered in Table HI were treated with 3 c.c. 
N/10 butyric acid for T5 minutes and washed well before 
■being placed in the NaOH solution. Afterwards they were 
Table II. 
(1) 3 c.c. N/10 butyric acid + 50 c.c. sea-water foi 
1 min. 
(-) Ditto, D25 min. 
(3) Ditto, 1'5 min. 
(4) Ditto, 1’75 min. 
(5) Ditto, 2 min. 
(6) Ditto, 2'25 min. 
(7) Ditto, 3'25 min. 
45°/oblastulse. 
