ARTIFICIAL PARTHENOGKNFSIS IN ECHINUS ESCULENTUS. 541 
The proportion of tannic acid added to 50 c.c. of sea-water 
and sugar was also varied (see 'I’able XI). In our later 
experiments we used T4 c.c. M/60 tannic acid followed by 
T5 c.c. N/10 ammonia to 50 c.c. of solution. The best time 
for allowing the reagents to act on the eggs is for one hour 
after adding the ammonia. Three quarters of an hour fails 
to stimulate many of the eggs to start cleavage, and an hour 
and a quarter materially increases the number of deformed 
blastulse. 
Table XI. — 10 c.c. Sea-water + 40 c.c. 1T3 M Sugar. 
(1) 1'2 c.c. M/60 tannic acid for 6 min. 
1'3 c.c. N/10 ammonia for 1 hr. 
(2) 1'4 c.c. M/60 tannic acid for 6 min. 
1'.5 c.c. N/lO ammonia for 1 hi-. 
(3) 1'6 c.c. M/60 tannic acid for 6 min. 
1’7 c.c. N/10 ammonia for 1 hr. 
(4) 1‘8 c.c. M/60 tannic acid for 6 min. 
T9 c.c. N/10 ammonia for 1 In-. 
30° /o eggs unchanged; some 
cytolysis and seiiaration of 
blastomeres ; 10 ° /q blas- 
tulse. 
40° /o blastulse. 
20°/q blastulai ; great sepa- 
ration of blastomeres. 
10° /o blastulaj ; more cyto 
lysis than (1), (2), or (3). 
Our final variation of Delage’s method is described below : 
(1) The eggs are placed in a solution of 100 c.c. sea-water 
-b 40 c.c. 1T3 M. cane-sugar + T4 c.c. M/60 tannic acid for 
six minutes. 
(2) T5 c.c. N/10 ammonia is added to the above solution 
and the eggs are left for one hour. 
(3) The bowl is filled up with sea- water and the eggs are 
washed with three or four changes of sea-water before being 
finally left in normal sea-water. 
At stage (3) the bowl has to be filled up with sea-water 
before the reagents can be drawn off, as the eggs float in the 
viscous sugary solution, but after adding sufficient sea-water 
they fall to the bottom. It is important to wash with three 
or four changes of water after the tannic acid, as traces of 
the latter left in the water cause a white precipitate to be 
thrown down. This precipitate only appears slowly, some- 
times not for two or three days. 
