ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 261 
It was easily discovered that, as in the egg of purpuratus, 
a neutral hypertonic solution cannot produce development in 
the egg of Polynoe; for this effect is possible only in alkaline 
hypertonic solution. To 50 c.c. of a neutral m/2 van’t Hoff 
solution +9 c.c. 25m NaCl there was added 0.5 c.c. N/10 
NaOH; another such hypertonic solution was prepared without 
the alkali. After two hours in these solutions the eggs were 
transferred to normal sea-water. Most of the eggs taken from 
the neutral hypertonic solution formed no membrane in normal 
sea-water; they did not extrude polar bodies, segment, or 
develop. On the other hand, about 1 per cent of the eggs that 
had been in the alkaline hypertonic solution segmented per- 
fectly regularly in the course of a few hours as far as the eight- 
cell stage, and the majority of the eggs developed into swimming 
larvae. The development of the eggs was generally quicker 
than in the case of unfertilized eggs exposed to hyperalkaline 
but not hypertonic sea-water. 
Again, eggs that remained between two and six hours in 
the neutral hypertonic solution did not develop when subse- 
quently transferred to ordinary sea-water. But when the 
unfertilized eggs of Polynoe were first put for two hours into 
a neutral hypertonic solution and then for not more than four 
hours into 50 ¢.c. sea-water+0.5 ¢c.c. N/10 NaOH, large num- 
bers of them developed into swimming larvae upon trans- 
ference to normal sea-water. But if the eggs were put for 
four hours into 50 ¢.c. sea-water+0.5 ¢.c. N/10 NaOH without 
being exposed to the hypertonic solution, as a rule no eggs, 
or only a few, developed.! 
It is hardly necessary to point out the analogy between the 
effect of alkaline and hypertonic sea-water upon the eggs of 
sea-urchins and of Polynoe. Like saponin, the alkali produces 
solution of the chorion and membrane formation in Polynoe. 
1! Loeb, ‘‘ Ueber die allgemeinen Methoden der kiinstlichen Parthenogenese,”’ 
Pfliiger’s Archiv, CXVIII, 572, 1907. 
