THE PARTHENOGENETIC EFFECT OF SPERM FIL- 

 TRATES, CONCENTRATED SPERM SUSPEN- 

 SIONS, AND SERUM OF CHITONS ON 

 THE OVA OF THE SEA-URCHIN, 

 STRONGYLOCENTROTUS 

 FRANCISCANUS. l 



MYRA M. SAMPSON, 



DEPARTMENT OF ZOOLOGY, SMITH COLLEGE, NORTHAMPTON, MASS., 



HOPKINS MARINE LABORATORY, PACIFIC GROVE, CALIFORNIA. 



AMER. Assoc. UNIV. WOMEN, BOSTON ALUMNA FELLOW. 



Kupelwieser (1906) reported that the unfertilized eggs of two 

 species of sea-urchins, Strongylocentrotus purpuratus and Strongy- 

 locenlrotus franciscanus, exposed to concentrated sperm or to 

 filtrates prepared from heated sperm of two species (?) of chiton, 

 formed fertilization membranes; and, if subsequently treated 

 with Loeb's hypertonic sea-water, developed. Loeb (1907 and 

 1908) obtained similar results with the blood serum of different 

 species of animals. In recent experiments I have obtained similar 

 effects with the ova of 5. franciscanus. In addition filtrates 

 prepared from suspensions of living sperm of the chiton, Kath- 

 arina tunicata, caused the formation of fertilization membranes 

 in ova of S. franciscanus. Subsequent treatment with hyper- 

 tonic sea-water led to the development of many of the ova in 

 which membranes appeared. 



These experiments were performed during the spring of 1921 

 at the Hopkins Marine Laboratory at Pacific Grove, California. 

 I wish to express here my appreciation of the hospitality extended 

 to me at this laboratory and my thanks to the Director, Dr. 

 Walter K. Fisher, for his generous assistance. 



MATERIAL. 



Within a few miles of the Laboratory, in protected situations 

 along the rocky coast , there is to be found an abundance of the 

 sea-urchins, S. franciscanus and 5. purpuratus and of the chitons, 

 Katharina tunicala, Ishnochilon magdalensis and Cryptochilon, 



1 Contributions from the Zoological Laboratory of Smith College No. 137. 



202 



