208 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
2. The existence and rdéle 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 
Fics. 59-62.—Collapse of the fertilization membrane if a liquid colloids 
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 
ege 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 
