ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 203 



however, acting as completely as it does in the sea-urchin egg 

 after membrane formation. 



4. Mead 1 observed that the addition of a small amount of 

 KC1 to the sea-water causes the eggs of Chaetopterus to throw 

 out their polar bodies, and the writer observed that the same 

 procedure causes these eggs to develop into larvae. 2 I had 

 already expressed the suspicion that these eggs develop into 

 larvae without segmentation. F. Lillie made sure of this fact 

 by a cytological examination of the eggs. 3 



All efforts to cause this egg to undergo development with 

 normal segmentation failed until Wasteneys and the writer 

 tried the effects of foreign blood serum. The eggs were put for 

 from 1| to 2J minutes into a mixture of 25 c.c. 3/8 m SrCl 2 + 

 25c.c. m/2 (NaCl+KCl+CaCl 2 ), then for 10 minutes into 

 ox serum diluted with its own volume of m/2 Ringer solution 

 and then for 30 minutes into hypertonic sea-water. Such eggs 

 when transferred back to normal sea-water segmented and de- 

 veloped into larvae. 4 They were usually not normal larvae, 

 inasmuch as they showed a tendency to stick to the glass and 

 to each other. Moreover, the cleavage cells of the same egg 

 fell apart easily. The method needs further improvement. 



5. Lefevre succeeded in causing artificial parthenogenesis 

 in the eggs of Thalassema mellita, a marine annelid of North 

 Carolina. 5 The eggs of this worm are fertilized in the oocyte 

 stage, just like those of Polynoe. The entry of the spermato- 

 zoon leads to the formation of a fertilization membrane; the 

 two polar bodies are then extruded, and segmentation and devel- 

 opment start after maturation is complete. Now Lefevre 

 found that when the unripe eggs of Thalassema are exposed to 



1 Mead, Biological Lectures delivered at Woods Hole, 1898. 

 2Loeb, Am. Jour. PhysioL, IV, 423, 1901. 



3 F. R. Lillie, Archiv f. Entwicklungsmechanik, XIV, 477, 1902. 



4 Loeb and Wasteneys, Science, XXXVI, 255, 1912. 



5 G. Lefevre, "Artificial Parthenogenesis in Thalassema mellita," Jour. Exper. 

 Zool, IV, 91, 1907. 



