50 E. E. JUST. 



development; eggs washed free of fertilizin lose their fertilizing 

 power; immature eggs and fertilized eggs show no fertilizin 

 reaction and are incapable of fertilization (and re-fertilization). 



Now, development of sea-urchin ova and of marine ova gener- 

 ally by chemical and physical agents is of course purely artificial; 

 it is at least debatable that these agents are as efficient tor 

 initiating development as specific sperm. In Nereis and in 

 Echinarachnius the volume of evidence is incontrovertible: only 

 those eggs in best condition (as shown by their fertilizin tests) 

 respond to artificial agents that initiate development. If eggs 

 from a given lot fail of fertilization the remainder of that lot 

 will not respond to artificial agents. Indeed, in both Nereis 

 and Echinarachnius the egg through washing and loss of ferti- 

 lizin loses its power to respond to warming (Nereis) or to butyric 

 acid (Echinarachnius) before it loses its power to respond to 

 sperm. Eggs with full fertilizin content most nearly ensure 

 success with artificial agents. 



Blood inhibits fertilization a truism to the embryologist ; 

 where marine ova are normally shed and insemination takes 

 place in the sea, it is generally found best to wash the eggs before 

 insemination. Normally shed eggs always give a high per cent, 

 of development; eggs cut or washed from the ovaries are not so 

 good. Thus, in Podarke and in Cumingia, for example, eggs 

 develop in greatest number if laid. The blood blocks fertiliza- 

 tion "by occupying the ovophile group of the fertilizin, thus 

 preventing action of the latter upon the egg by union with egg 

 receptors" (Lillie). It probably acts m the same way in artificial 

 initiation of development. 



In Nereis and in Echinarachnius blood inhibits both fertiliza- 

 tion and artificial initiation of development. In Arbacia Lillie 

 found that blood inhibits fertilization while Heilbrunn observed 

 that it also inhibits membrane formation. The worker, there- 

 fore, who studies "artificial parthenogenesis" is between Scylla 

 and Charybdis either he will not wash the eggs and thus have 

 blood inhibitor present, or he will wash too much and so bring 

 about too great secretion of fertilizin. This may seem fanciful 

 to some but experience with Nereis, Platynereis and Echinarach- 

 nius teaches that the egg is anything but an inert cell; for sue- 



