288 WALTER E. CARREY. 



from the eggs of Strongylocentrotus purpuratus and that after 

 subsequent treatment with sodium hydroxide and calcium 

 chloride, starfish sperm caused the formation of fertilization 

 membranes and induced development. F. R. Lillie 1 found that 

 Arbacia "eggs are fertilizable" after complete removal of the 

 jelly by Loeb's method. Loeb and Kupelwieser 2 caused the 

 formation of fertilization membranes by treating eggs with buty- 

 ric acid ; these were freed from every vestige of membrane and 

 jelly was removed by shaking, yet upon insemination they were 

 able to form new fertilization membranes. Moore 3 noted that 

 egg fragments, produced by shaking, formed membranes upon 

 entrance of the spermatozoon. These observations indicate that 

 the egg jelly is not essential for the formation of the fertilization 

 membrane. 



II. The facts considered in the preceding section make us 

 doubt the validity of the hypothesis advanced by McClendon 

 that the fertilization membrane is formed by the process of 

 precipitation due to the contact of two colloids carrying opposite 

 electric charges; viz., the egg jelly which McClendon states is 

 electro-negative and another colloid (membranogen) derived from 

 the egg which he found to be electropositive. This view is 

 rendered quite untenable when we consider the fact that fertiliza- 

 tion membranes are formed about echinoderm eggs by Loeb's 

 well-known methods of inducing artificial parthenogenesis by 

 treatment with weak fatty acids. These acids act only after 

 penetrating the egg-jelly in the course of which event they impart 

 to that colloid the positive electric charge of the dominant 

 hydrogen ion; they therefore have the same charge as the 

 colloids of the egg and the requisite conditions for precipitation 

 of colloids do not exist. 



It has furthermore been shown that in the chemical fertiliza- 

 tion of Asterias eggs either acids or alkalies may be used to induce 

 membrane formation. The electric charge of the jelly is positive 

 when acids are used and negative with alkalis; obviously the 

 charge is not of opposite sign to that of the egg substance 

 (membranogen) in both cases. 



1 Lillie, F. R., BIOL. BULL., 1915, XXVIII., 24. 



- Kupfelweiser, H., Arch. f. Enlw., 1909, XXVII., 434. 



3 Moore, A. R., Univ. California Pub., 1912, IV., 89. 



