170 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
formation of abnormal chemical products in the egg; or the 
oxidations lead to physical or morphological modifications in 
the egg, which cause its disintegration when it is put back 
into normal sea-water. We can imagine that chloral hydrate 
acts favorably by suppressing certain morphological changes 
in the egg. 
While it is not always possible to induce artificial partheno- 
genesis by the purely osmotic method, the destruction of the 
eggs by this method and the prevention or retardation of this 
destruction by lack of oxygen always succeeds. 
6. In 1908 Delage published a method of artificial partheno- 
genesis which gave good results. The unfertilized eggs were 
put into a mixture of 50 c.c. of a cane-sugar solution and sea- 
water to which he added 23 drops of a N/10 tannic-acid solution 
and 30 drops of a N/10 solution of NH,OH. The concentra- 
tion of the sugar solution was 1.135 N. He used 15 c.c. sea- 
water and 35 c.c. cane-sugar solution.! In reality this method 
is identical with my method of combining alkaline and hy- 
pertonic solutions simultaneously. The 1.135 N sugar solution 
is strongly hypertonic (see chap. xiii). The ammonia is in 
excess of the tannic acid and NH,OH is, as we have seen, one 
of the bases which diffuses easily into the egg, and hence is 
very efficient in the production of artificial parthenogenesis. 
Since any hypertonic solution with the proper amount of 
NH,OH acts in the same way as Delage’s solution, neither 
the presence of tannic acid nor of sugar is essential. 
Shearer and Miss Lloyd? have used Delage’s mixture in the 
place of the hypertonic sea-water in my “improved” method. 
They produced membrane formation in the unfertilized eggs 
of Hchinus with butyric acid. Instead of putting them into 
hypertonic sea-water afterward, they put them for one hour 
1 Delage, ‘‘ Les vrais facteurs de la parthénogénése expérimentale,” Arch. de 
Zool. expér. et gén., 4me sér., VII, 446, 1908. 
? Shearer and Miss Lloyd, Quarterly Jour. Microscopical Science, LVIII, 523, 
1913. 
