FERTILIZATION REACTION IN ECHINARACttNIUS PARMA. 35 



enter these stale eggs likewise; for example, in Platynereis (Just, 

 '156) sperm not only enter but come into apposition with the 

 female nucleus without inducing development though matura- 

 tion has been complete. Through the work of Lillie on Arbacia 

 these phenomena may be interpreted: immature eggs, stale 

 eggs and fertilized eggs produce no fertilizin; they are incapable 

 of fertilization. One cannot help but postulate a causal con- 

 nection. Much the same interpretation is possible in Nereis 

 and Platynereis. In Echinarachnius the process is in every way 

 similar to that in Arbacia. Whatever prejudice one may have to 

 the fertilizin theory of fertilization because of the immunological 

 terminology, the proved facts one must admit. At the very 

 least, fertilizin is an index to fertilization capacity. 



Again, eggs show a period during which they are most sus- 

 ceptible to agents that initiate development. This has been 

 most clearly shown for the starfish by Mathews and by R. S. 

 Lillie. It is generally known that the eggs of some females 

 respond more readily to agents that initiate development than 

 others. In the Nereis (Just, 'i5a) one may observe a very striking 

 behavior of the egg to warmed sea-water. From a female 

 quickly dried, dry eggs are taken and divided into two lots. 

 One lot is placed in a small quantity of sea-water at 33 C. and 

 the other into ordinary sea-water. Those eggs in warm sea- 

 water will form jelly, maturate and cleave, the resulting embryos 

 closely simulating the normal. If the eggs in ordinary sea- 

 water be transferred to warmed sea-water they do not even form 

 jelly. Nothing is more striking than the comparison between 

 two lots of Nereis eggs that have been subjected to warming with 

 and without previous exposure to ordinary sea-water: the dry 

 eggs are in a thick mat of jelly, the washed eggs closely crowded 

 together without any jelly formed. In Nereis, then, the egg 

 must have its full content of fertilizin in order to respond to 

 warming asa means of artificial parthenogenesis: it loses its power 

 for initiation of development by artificial means before it loses 

 its fertilizing power. Muscle, nerve and gland respond to arti- 

 ficial stimulation, but the normal mode is most effective. So 

 the sperm is the most efficient activator for the egg. In Nereis 

 the best time for artificial parthenogenesis is the time of greatest 

 fertilizin content. 



