FERTILIZATION ON PARTHENOGENESIS. 14! 



The fundamental questions arising in consideration of these 

 and other factors of fertilization are very evident. They aim 

 at the very heart of the problem. It is necessary that \ve shall 

 not lose sight of the distinction between penetration of the egg 

 by the spermatozoon and the fertilization reaction; it is with 

 the latter that we are more intimately concerned at this time. 

 What then aie the conditions within the egg that permit or pro- 

 hibit fertilization? Is a reactivation of the egg or substances 

 within the egg possible by the use of a different activator or can 

 fertilization be superposed on parthenogenesis? 



This problem was suggested to me by Professor Lillie and the 

 experimental part was conducted under his supervision during 

 the summers of 1914-15 at Woods Hole, Mass. It gives me 

 great pleasure to express my indebtedness to him for his many 

 suggestions and kindly criticisms during the progress of the 

 work and also for a table in the Marine Biological laboratory. 

 The examination of Preserved Material was conducted in the 

 Hull zoological laboratory at the University of Chicago. 



II. MATERIAL AND METHODS. 



The writer's observations have been confined entirely to the 

 Atlantic sea urchin (Arbacia punctiilata) . Fresh material from 

 the live car was received daily and kept in aquaria of running 

 sea water. Eggs for the experiments were obtained in the 

 usual manner by cutting around the edge of the leathery oral 

 disc and removing the ovaries entire to a clean ringer bowl. The 

 ovaries were cut up and fresh sea water added and the whole 

 poured through cheese cloth. This allows the eggs to pass 

 through, and retains on the filter the pieces of ovarian tissue. 

 When the eggs had settled to the bottom of the dish the super- 

 natant sea water was poured off and replaced by fresh sea water 

 (200 C.C.-3OO c.c.) . This process of washing was usually repeated 

 three times and eggs were removed from the stock for the indi- 

 vidual experiments. For every experiment a control was also 

 set aside. 



Sperm ordinarily was easily obtained by allowing the males 

 to shed the solid sperm into clean dry Syracuse dishes. This 

 solid or "dry" sperm served as a stock supply from which the 

 suspensions were made as needed. 



