268 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
NaOH. Some of the eggs that had been exposed to solutions 
containing more NaOH did develop into larvae; the percentage 
of larvae varied according to the alkalinity of the solution and 
the time the egg was exposed to the solution. Many of the 
eggs that had been 2% hours in the hypertonic solution con- 
taining 0.8 c.c. of NaOH, or 2 hours in that containing 0.4 ¢.c., 
developed into larvae.! 
Hence it can be seen that just as in the case of the eggs of 
purpuratus and of Polynoe, the hypertonic solution as a rule only 
affects the eggs of Lottia when a certain degree of concentration 
of hydroxylions (about 107° N) has been reached. Further, it 
is also clear that when the concentration of hydroxylions in the 
hypertonic solution is higher than in sea-water, the number of 
larvae formed also increases. But in this case also, as in the 
experiments with the eggs of S. purpuratus, the optimal con- 
centration of hydroxylions for the production of larvae is sub- 
ject to large variations with the eggs of different females. 
The second fact brought out by these experiments is the 
importance of oxygen. In flat dishes (that are covered against 
evaporation of the sea-water) in which the eggs lie close to the 
surface of the water, the number of eggs that develop is appreci- 
ably higher than in dishes in which the eggs are covered with a 
deep layer of sea-water. 
Finally, it is a point of interest that no visible membrane 
formation takes place in these forms. Im this respect the eggs 
behave differently from those hitherto discussed. 
Attempts to separate by an interval of time the effect of the 
alkali and the raising of the osmotic pressure, as can be done 
with the eggs of the sea-urchin and of Polynoe, have not yet 
proved successful with Lotta. Moreover, development is not 
produced by treatment with alkali alone. 
In all these experiments the eggs developed practically 
1 Loeb, ‘‘ Ueber die ailgemeinen Methoden der kiinstlichen Parthenogenese,”’ 
op. cit. 
