260 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
eggs will develop into larvae without segmentation. In one 
experiment the unfertilized eggs of a female were placed in 
50 c.c. of sea-water+1.5 ¢.c. N/10 NaOH and left for some time 
in that solution. Four hours later all the eggs had formed a 
definite membrane and extruded both polar bodies. After eight 
hours a small number of the eggs were in the two-cell stage— 
cleavage was quite normal—but the rest remained undivided. 
Twenty-four to forty-eight hours after the start of the experi- 
ment the majority of the eggs had developed into swimming 
larvae. But, externally, segmentation did not appear to have 
extended beyond the two- or four-cell stage. The control eggs 
that had been left in ordinary sea-water had not matured, and 
in the course of twenty-four hours they fell to pieces. This 
oft-repeated experiment proves, therefore, that the unfertilized 
eges of Polynoe can be made to mature and develop into larvae 
by exposing them for some time to hyperalkaline sea-water. 
But there is one important consideration that must be taken 
into account, and that is a favorable supply of oxygen. The 
eggs developed in large numbers only when contained in lightly 
covered watch glasses, while the eggs left in the big dish in 
which they were separated from the air by some 2 cm. of water 
matured and developed in much smaller quantities. Perhaps, 
too, the neutralization of surplus alkali by the carbonic acid 
of the air is effected much more quickly in the watch glass 
than in the larger dish. I convinced myself, however, that if 
the eggs are transferred from the hyperalkaline to normal 
sea-water, the formation of larvae occurs only if the eggs have 
been at least from four to six hours in hyperalkaline sea-water ; 
and even then the results are much worse than when the eggs 
remain all the time in the hyperalkaline solution. If, however, 
the treatment with a hypertonic solution was combined with 
that by alkali, less alkali could be used and more eggs segmented 
and the segmentation advanced farther (especially in the case 
of weak bases). 
