AUTHOR'S ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, FEBRUARY 7 



ON THE DEVELOPMENT OF THE SPONTANEOUSLY 



PARTHENOGENETIC EGGS OF ASTERINA 



(PATIRIA) MINI ATA. 



H. H. NEWMAX.i 



INTRODUCTION. 



While engaged in a series of experiments on echinoderm hy- 

 bridology, which I was conducting during the months of April 

 and May, 1920, at Pacific Grove, California, I was forcibly struck 

 by the frequency with which spontaneous parthenogenesis occurs 

 in the starfish, Astcrina (Patina*) minata. When I use the term 

 " spontaneous," I mean that eggs were in no way treated either 

 by physical or by chemical agents. Precautions were taken, 

 moreover, to prevent accidental fertilization. The procedure was 

 as follows : 



Sea water, brought in from the open sea and therefore free 

 from the chemical impurities present in sea water that has been 

 pumped through metal pipes, was allowed to stand at least four 

 days at laboratory temperatures, which during the month of May 

 ranged from 16 to 19 C. It is certain that no sperms could 

 live for this length of time in sea water. This method is chosen 

 in preference to Loeb's practise of heating the sea water to 60 

 C. for some time, because it involves no possible chemical 

 changes in the sea water nor any driving out of oxygen. Before 

 opening a starfish, it was scrubbed thoroughly in cold running 

 fresh water and rinsed in a strong stream of fresh water. In 

 case the animal proved to be a male it was discarded, and hands 

 and instruments were scrubbed in fresh water before touching 

 another starfish. If the animal proved to be a ripe female the 

 ovaries were gently shaken into a finger-bowl containing 150 c.c. 

 of the sea water prepared for the purpose and the bowl was cov- 

 ered with a clean glass plate and placed upon a table out of reach 



i From the Hopkins Marine Station of Leland Stanford, Jr. University 

 and the Hull Zoological Laboratory of the University of Chicago. 



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