XXVII 



EXPERIMENTS WITH THE EGGS OF MOLLUSCS 



In 1902 Kostanecki succeeded in producing the early seg- 

 mentation stages (two to four cells) in the unfertilized eggs of a 

 mollusc (Madra), by exposing them for two hours to hypertonic 

 sea-water.' In 1903 the writer showed that the unfertilized eggs 

 of another mollusc, Lottia gigantea, and of several forms of 

 Acmaea can be made to develop into swimming larvae by 

 treating them with hypertonic sea-water.^ The method consists, 

 in principle, of placing the eggs for two hours in a mixture 

 of 50 c.c. of sea-water -|- 10 c.c. 2| m NaCl. The number of 

 larvae that developed was always small (only about 2 to 5 

 per cent of the eggs), and their vitaUty was low. As a rule 

 they succumbed after thirty-six to forty-eight hours. After I 

 had recognized the part played by bases in the actiyation of the 

 eggs of the sea-urchin, it next occurred to me to find out whether 

 the osmotic causation t)f development in Lottia is also acceler^ 

 ated or improved if this hypertonic solution is rendered alkaUne. 

 This was found to be true. Thus to 50 c.c. of (neutral) m/2 

 van't Hoff's solution -f- 12 c.c. of 2^ m NaCl were added in 

 different bowls 0, 0.1, 0.2, 0.4, and 0.8 c.c. N/10 NaOH. 

 Among these solutions the eggs of a Lottia were distributed 

 after being washed in a neutral solution (temperature 17.5° C). 

 Samples of the eggs were transferred to normal sea-water after 

 If, 2j, 2j, 3j, and 3f hours respectively. The eggs exposed 

 to neutral hypertonic solution did not develop, and the same 

 was the case with eggs that had been treated with 0.1 c.c. 



1 Kostanecki, " Zytologlsche Studien an ktiustlich parthenogenetisch sich 

 entwickelnden Eiem von Mactra," Arch. /. mikroscop, Anat. u. Entwicklungsgesch., 

 LXIV, 1, 1904. 



2 Loeb, University of California Publications, Physiology, 1,7, 1903 ; Untersuch- 

 ungen ueher kttnstliche Parihenogenese, p. 283. 



267 



