FERTILIZATION MEMBRANE OF ARBACIA. 239 



formation is not, then, a question of presence or absence of jelly 

 but is dependent on the time the eggs have stood. We may 

 imagine this to be due to the loss of some membrane-forming 

 material from the eggs which much more readily takes place 

 when the mechanical hindrance of the jelly is removed. 1 



These experiments point against the view that the fertilization 

 membrane is a precipitation membrane. 



BIBLIOGRAPHY. 

 Elder, . 



'13 Arch. f. Entwick., 35, 195. 

 Harvey, E. N. 



'10 J. Exp. Zool., 8, 365. 

 Kite, G. L. 



'12 Science, n. s., 36, 562. 

 Lillie, F. R. 



'14 J. Exp. Zool., 16, 550. 

 Loeb, J. 



'03 Pfltiger's Arch., 365, 59. 

 McClendon, J. F. 



'12 Science, n.s., 33, 387. 



'14 Zeit. f. physiol. chem. biol., i, 163. 



1 According to Kite ('12) membrane formation is merely the swelling of a fine 

 invisible (unless stained) vitelline membrane together with a change of its optical 

 properties. If that is true the inability of eggs which have stood for some time with- 

 out jelly to form fertilization membranes would seem to be due to a loss, through 

 solution, of the vitelline membrane. 



