ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 201 



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. 2J m 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.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.c. sea-water+0.5 c.c. N/10 NaOH without 

 being exposed to the hypertonic solution, as a rule no eggs, 

 or only a few, developed. 1 



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 kunstlichen Parthenogenese," 

 Pfliiger's Archiv, CXVIII, 572, 1907. 



