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 4 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. 1 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 4 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 4 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 2 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 Echinus 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 parthenogenese experimental, " .4rc/i. de 

 Zool. exper. et gen., 4me ser., VII, 446, 1908. 



2 Shearer and Miss Lloyd, Quarterly Jour. Microscopical Science, LVIII, 523, 

 1913. 



