FERTILIZATION MEMBRANE OF ASTERIAS AND ARBACIA EGGS. 289 



Upon treatment- with acids the egg jelly swells perceptibly 

 and also removes the acid from solution either by adsorbing it 

 or by chemically uniting with it. In either event the jelly 

 becomes electropositive. The fixation of the acid is shown in 

 the following experiments. 



Ripe eggs from Asterias ovaries are shed in sea water and 

 allowed to settle to the bottom of a graduated cylinder. The 

 supernatant liquid is decanted and enough fresh sea water added 

 to the mass of eggs to equal three times their volume. The 

 cylinder is actively shaken and the eggs again are allowed to 

 settle. The clear supernatant fluid containing a considerable 

 amount of the jelly is now decanted off and an equal volume 

 of N/$oo butyric acid added. Fresh Asterias egg do not form 

 fertilization membranes in this acid-jelly mixture but do so in 

 a control solution of N/i,ooo butyric acid in sea water. On the 

 other hand fertilization membranes are formed at once in the 

 acid-jelly mixture after the further addition of an equal volume 

 of N/SOO butyric acid sea water, thus indicating clearly that the 

 initial effect of the jelly is to remove the acid from solution and 

 that membrane formation is induced only when acid is present 

 in excess of the amount necessary to saturate the jelly. Neglect 

 in the observance of this precaution doubtless has been the cause 

 of many failures to obtain good artificial fertilization by this 

 method in case large masses of eggs have been added to small 

 amounts of acid sea water. Loeb 1 cautioned against such a loose 

 procedure. Under such conditions the relatively large amount 

 of adherent jelly fixes the acid and prevents it from acting on 

 the eggs. 



III. The formation of fertilization membranes after the com- 

 plete removal of the jelly indicates the origin of this structure 

 from the egg. The following experiment furnishes a simple but 

 equally conclusive mechanical demonstration of this fact. Fer- 

 tilization of the eggs of Asterias either by sperm or by artificial 

 means such as acid or heat (30-33 C.) is possible not only after 

 maturation but also earlier, when the nuclear membrane about 

 the germinal vesicle just begins to fade (De Lage 2 ) ; in fact I have 



1 Loeb, ]., "Artificial Parthenogenesis" (Chicago), 1913, 69. 

 , 2 DeLage, Y., Arch, de zoo/, exper. et gen., ser. 3, IX., 285. 



