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ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 259 
not divide, and did not in this experiment develop into larvae. 
On the other hand, practically all of the eggs treated with 
saponin that had been two hours and twenty minutes in the 
hypertonic sea-water segmented, but reached only the eight-cell 
stage in four hours after removal from the hypertonic sea-water. 
Four hours later these eggs had reached the trochophore stage 
and were swimming about. But it is doubtful whether they 
had undergone any further segmentation. Eggs that had been 
exposed only to hypertonic sea-water, without previous mem- 
brane formation under the influence of saponin, did not develop 
into larvae. This experiment was repeated, and it was then 
found that, though by producing membrane formation by 
means of saponin a few eggs of Polynoe can indeed be made to 
develop into larvae, a subsequent exposure to hypertonic sea- 
water causes many more eggs to develop. The rate of develop- 
ment is also increased by this method. The analogy in behavior 
between the eggs of Polynoe and of the sea-urchin is obvious, 
although not complete, since the sea-urchin eggs all develop 
in this case by segmentation, while the eggs of Poiynoe develop 
without or only with incomplete segmentation. 
The eggs of Polynoe resemble the eggs of the starfish, in 
so far as the membrane formation suffices for the causation of 
development of some eggs, and in so far as the addition of the 
second corrective factor increases the number of eggs capable 
of development. 
2. There is yet another method by which the unfertilized 
eggs of Polynoe can be made to develop. This is by raising the 
alkalinity of the sea-water.’ 
If the concentration of the hydroxylions in sea-water be 
raised by the addition of a considerable amount of sodium 
hydrate, not only can the unfertilized eggs of Polynoe be induced 
to ripen, but a small percentage of them will segment into two 
or four cells; and sometimes a large percentage or even all the 
1 Loeb, ‘‘ Ueber die allgemeinen Methoden der kiinstlichen Parthenogenese,”’ 
Pfliiger’s Archiv, CXVIII, 572, 1907. 
