ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 665 
drawn above, that the unfertilized eggs of Cheetopterus can- 
not develop into a trochophore if left in normal sea-water. 
A small number of K ions, however, is able to cause them 
to develop parthenogenetically. If the eggs are put for 
three minutes into a mixture of 2 c.c. 242 KCl+ 98 c.c. sea- 
water, they are able to develop parthenogenetically. If the 
sea-water contains fewer K ions, ec. g., if we add 1 c.c. 24n 
KCl to 99 ¢.c. sea-water, the eggs must remain longer in the 
solution. Finally, if we add only $.c.c. 24n KCl to 994 c.c. 
sea-water, the eggs are not able to develop parthenogeneti- 
cally, no matter how long they are left in such a solution. 
They can be caused to reach the trochophore stage by a pure 
KCI solution of considerably lower osmotic pressure than 
that of sea-water. If the sea-water contained only a slightly 
greater proportion of K, we should find that Cheetopterus 
was “normally” parthenogenetic. 
IV. ARTIFICIAL PARTHENOGENESIS PRODUCED BY A SLIGHT 
ADDITION OF HCL TO SEA-WATER 
In my experiments on Echinoderms, I had found that 
the addition of a small quantity of acid or alkali causes the 
unfertilized eggs of sea-urchins to segment much more 
quickly than is the case in normal sea-water. I intended to 
try the effects of the same agencies on the eggs of Chatop- 
terus. The sea-water is slightly alkaline, 7. ¢., has a small 
quantity of free hydroxl ions in solution.’ If we add more 
alkali, the number of the hydroxylions is but slightly 
increased, inasmuch as a precipitate of Mg(HO), is formed. 
With acids it is different. If we add a certain small amount, 
the sea-water becomes neutral; and if we add more, it 
becomes acid according to the amount and degree of disso- 
ciation of the acid used. All the sea-water in these experi- 
ments was sterilized. 
1 This was the common view held at that time. I have since found that sea-water 
is neutral. [1903] 
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