262 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



This results in the extrusion of the polar bodies and develop- 

 ment. But the effect of the alkaline solution is enhanced by 

 the treatment of the eggs with hypertonic sea-water. 



3. We have already stated that the weak bases are much 

 more efficient in causing artificial parthenogenesis than the 

 strong bases. The best effects were produced with the amines, 

 especially butylamine and benzylamine ; next in efficiency were 

 NH 4 OH and trimethylamine, and the weakest effects were pro- 

 duced by the strong bases NaOH and tetraethylammonium- 

 hydroxide. 



To give an example: to 50 c.c. hypertonic sea-water (100 c.c. 

 sea-water +1 8 c.c. 2| m NaCl) were added 1.5 c.c. N/10 

 NaOH, benzylamine, and NH 4 OH, respectively. Of the eggs 

 that had been forty-five minutes in benzylamine, 40 per cent 

 developed; the same result was produced by an exposure in 

 NH 4 OH of 80 minutes. An exposure of 115 minutes in NaOH 

 gave a much smaller number of larvae. Those treated with 

 NaOH reached the swimming stage as a rule much later than 

 those treated with an amine. The eggs treated with the amine, 

 especially with butylamine and benzylamine, segmented almost 

 normally, although much more slowly than the eggs fertilized 

 with sperm. 



In repeating these experiments with sea-water made alkaline 

 (but not hypertonic), the writer was struck with the fact 

 that the eggs developed into larvae without segmentation, and 

 very slowly, while with both hypertonic and hyperalkaline 

 sea-water they segmented and developed more rapidly into 

 larvae, though still more slowly than the eggs fertilized by sperm. 



It is obvious that when the hypertonic solution acts in this 

 way it makes the development more normal. This may also 

 be a " second factor" effect. While the eggs of Polynoe do 

 not directly disintegrate after artificial membrane formation, 

 they show their abnormal state by developing without segmen- 

 tation. The hypertonic solution remedies this defect, without, 



