THE MECHANISM OF MEMBRANE FORMATION AND 

 OTHER EARLY CHANGES IN DEVELOPING SEA- 

 URCHINS' EGGS AS BEARING ON THE PROBLEM 

 OF ARTIFICIAL PARTHENOGENESIS 



E. NEWTON HARVEY 



Columbia University 

 With Two Figures 



The first visible change occurring in manyeggsafter the entrance 

 of a spermatozoon is the appearance, at the peripherv of the egg, 

 of a fertihzation membrane. Although observed and discussed 

 by many authors, very h'ttle experimental work has been done on 

 the mechanism of its formation. Yet such an investigation may 

 give a clue to the nature of the change initiating development. 



This summer (iQog) a study of membrane formation in Echino- 

 derm eggs was undertaken. The experimental work was per- 

 formed in part at the Biological Laboratory of the Carnegie 

 Institution at Tortugas, Florida, and in part at the Marine Bio- 

 logical Laboratory at Woods Hole, Massachusetts. I wish to 

 express my thanks to Dr. Ralph Lillie for the use of some 

 reagents and to the Wistar Institute of Anatomy for a table at 

 the latter station. I am also indebted to Dr. T. H. Morgan for 

 very kindly criticising this paper. 



The forms experimented on at Tortugas were Toxopneustes 

 variegatus and to a less extent Hipponoe esculenta. At Woods 

 Hole Arbacia punctulata was used. 



I shall discuss the early changes taking place in developing eggs 

 under seven heads, viz: 



1 The efficiency of acetic acid m forming membranes at 

 different temperatures. 



2 The mechanism of membrane^ formation. 



' Unless otherwise stated, by membrane, the fertihzation or vitelline membrane is meant. The sur- 

 face film or plasma membrane of the egg is spoken of as the egg membrane. The two have very 

 different properties both chemical and physical. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 8, NO. 4. 



