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 
molluse (Mactra), 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. of sea-water+10c.c. 24m NaCl. The number of 
larvae that developed was always small (only about 2 to 5 
per cent of the eggs), and their vitality 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 activation of the 
eggs of the sea-urchin, it next occurred to me to find out whether 
the osmotic causation of development in Lofttia is also acceler- 
ated or improved if this hypertonic solution is rendered alkaline. 
This was found to be true. Thus to 50 c.c. of (neutral) m/2 
van’t Hoff’s solution+12¢.e. of 25m 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 
13, 21, 23, 34, and 32 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, ‘‘Zytologische Studien an kiinstlich parthenogenetisch sich 
entwickelnden Eiern von Mactra,” Arch. f. mikroscop. Anat. u. Entwicklungsgesch., 
LXIV, 1, 1904. 
2 Loeb, University of California Publications, Physiology, I, 7, 1903; Untersuch- 
ungen ueber kiinstliche Parthenogenese, p. 283. 
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