ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 665 



drawn above, that the unfertilized eggs of Chsetopterus 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. 2^n KC1 -(- 98 c.c. sea- 

 water, they are able to develop parthenogenetically. If the 

 sea-water contains fewer K ions, e. g., if we add 1 c.c. 2^ 

 KC1 to 99 c.c. sea- water, the eggs must remain longer in the 

 solution. Finally, if we add only ^ c.c. 2^n KC1 to 99| 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 

 KC1 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 Chsetopterus 

 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 Cha3top- 

 terus. The sea- water is slightly alkaline, i. e., has a small 

 quantity of free hydroxl ions in solution.' If we add more 

 alkali, the number of the hydroxyl ions is but slightly 

 increased, inasmuch as a precipitate of Mg(HO) 3 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] 



