208 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



2. The existence and role of this colloid becomes clear 

 through the following experiments. When we put fertilized 

 eggs or eggs with a butyric-acid membrane into sea-water whose 

 concentration is raised through the addition of salt or sugar, 

 the diameter of the fertilization membrane remains unaltered 

 (while the protoplasm of the egg shrinks) . If we dilute the sea- 

 water by adding distilled water, the diameter of the fertilization 



Fig. 59 



Fig. 60 



Fig. 61 Fig. 62 



FIGS. 59-62. Collapse of the fertilization membrane if a liquid colloid; 

 e.g., some liquid white of egg, is added to the sea-water. In Figs. 59 and 60 very 

 little, in Figs. 61 and 62 more, white of egg was added to the sea-water. When 

 the eggs are replaced in normal sea-water the normal membrane is re-established 

 at once. 



membrane also remains unaltered while the protoplasm of the 

 egg swells. This proves that the fertilization membrane is 

 permeable for water, sugar, and salts, while the protoplasm of 

 the egg is not. 



If we add, however, any colloidal substance, e.g., white of 

 egg or blood, or even tannic acid, to the sea-water, the membrane 

 collapses at once (Figs. 59-62). If the eggs are put into sea- 

 water again which is free from colloids, the membrane becomes 

 spherical again almost at once. This proves that the membrane 



