434 MARIE A. HINRICHS. 



come permanent, due to the increased adhesiveness and loss of 

 motility of individual sperm. Also, radiated sperm produce 

 reticular, stringy masses on the addition of normal egg-water. 

 Here again, the increased stickiness of the sperm and the loss of 

 motility are a result of radiation. 



I wish to acknowledge my gratitude to Dr. R. S. Lillie for his 

 cooperation in the study of this problem. The experiments were 

 made at Woods Hole during the summer of 1926. 



Conclusions. I. Earlier work with ultraviolet radiation and 

 Arbacia germ cells has shown the following results: (a) Radiated 

 eggs fertilized by normal sperm, normal eggs fertilized by radi- 

 ated sperm, or radiated zygotes produce differentially modified 

 larvae, (b) Radiation of normal sperm causes a reduction and loss 

 of motility and fertilizing power, and (c) Radiation of normal 

 sperm suspensions causes sperm to form irregular, permanent ag- 

 gregates. Continued radiation kills the sperm. 



II. The present experiments have added the following: 



(a) The radiation of normal eggs produces at first a slight in- 

 crease, then a decrease, and finally a complete loss of the power 

 of producing fertilizin. There is a parallel loss of viability of the 

 eggs as measured by their fertilizability and ability to develop 

 normally. 



(b) The radiation of normal egg- water produces a fading of 

 echinochrome pigment, and a reduction of the agglutinating power 

 of fertilizin. The two are affected at different rates. The addi- 

 tive effect of temperature and radiation is more rapid in its ac- 

 tion upon fertilizin, than upon echinochrome. 



(V) The agglutinating power of egg-water is lost before its 

 sperm-stimulating power, suggesting that two distinct substances 

 may be concerned. 



(d) There is an optimum pH range, around the point of neu- 

 trality, for the agglutinating action of egg-water. A similar 

 range is present for the adsorption of fertilizin by charcoal. Ad- 

 sorbed fertilizin retains some of its agglutinating power. The 

 enzyme-like character of fertilizin is indicated. Adsorbed ferti- 

 lizin may be displaced from adsorption by a slight acidification, 

 but not by the addition of surface-active compounds. Fertilizin 

 has a high adsorption constant. For this reason, fertilizin is prob- 



