650 STUDIES IN GENERAL PHYSIOLOGY 
All the sea-water had been sterilized the previous day by 
heating it to a temperature of 80°; one part (a) of the eggs 
remained one hour, a second part (6) one hour and twenty 
minutes in these solutions. 
The first four solutions yielded numerous swimming 
trochophores; their number was greatest in the first two 
solutions. Lot aof the MgCl, solution yielded no swimming 
blastule, but lot b had a few. The control eggs were com- 
pletely undeveloped, with the exception that after about ten 
hours a few showed the beginning of a segmentation, which 
in no case led to the formation of more than from 4 to 6 
cells. During the next forty-eight hours no further develop- 
ment occurred, and the eggs died and disintegrated. Accord- 
ing to this experiment the unfertilized eggs of Cheetopterus 
are not able to develop in normal sea-water. They can, 
however, be caused to develop into trochophores if exposed 
for about an hour to sea-water whose concentration has been 
raised through the addition of the right quantity of KCl or 
NaCl. 
Third series.—The next task was to ascertain how much 
the osmotic pressure of the sea-water must be raised in 
order to bring about the parthenogenetic development, and 
whether the increase in osmotic pressure necessary for this 
purpose was the same in each case. The solutions used 
were as follows: 
(1) 10 ec. 24n KCl +90 c¢.c. sea-water 
(2) 12h ec. 24n KCl +873 “ 
(3) 380 ee. 2 2 cane-sugar-+70 
(4) 123 cc. 24 NaCl +874 $ 
(5) Normal sea-water (control) 
The osmotic pressure in solutions 2, 8, and 4 was about 
the same. The.eggs remained sixty-five minutes in these 
solutions, and were then put back into normal sea-water. 
While a great number of the eggs that had been in solutions 
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