NOTE ON THE NATURE AND SOURCE OF 



"PURPLE X." 1 



ALVALYN E. WOODWARD. 



In the summer of 1913, Dr. O. C. Glaser ('14) found (i) that 

 if a suspension of Arbacia sperm be boiled it turns purple, (2) 

 that this purple color disappears if the boiled suspension be allowed 

 to stand over night, and (3) that initiation of development in 

 Arbacia eggs, either by sperm or by egg secretion, can be in- 

 hibited by the addition to the eggs of this boiled suspension 

 so long as it is purple. This purple substance, he provisionally 

 designated as "purple x." 



I. SOURCE OF "PURPLE X." 



In 1914, while working with various inhibitors of fertilization 

 in Arbacia, I wished to use "purple x" and found that it did 

 not always appear when Arbacia sperm was boiled. This 

 naturally led to a search for the source of the substance. Sperm 

 was obtained from a large number of males. Each one was 

 rinsed in fresh water, and after the peristome was cut, placed 

 aboral side down in a clean dry watch-glass, until the seminal 

 fluid had been freely shed. A portion of the sperm from each 

 animal was then mixed with filtered sea-water and examined under 

 the microscope and a second, larger portion of each was boiled. 

 It was found that, as a rule, the suspensions which showed fewest 

 foreign cells blood-cells or fragments of organs were least 

 likely to form "purple x." Suspensions which appeared, under 

 the microscope, fairly free from foreign cells, could be depended 

 upon to give a colorless filtrate when boiled. 



What, then, is the impurity which produces "purple x"? 

 By a series of experiments properly checked and repeated, I was 

 able to eliminate successively, the filtered perivisceral fluid 

 (serum), the blood clot which had been washed in sea-water 



1 From the Marine Biological Laboratory at Woods Hole and the Zoological 

 Laboratory of the University of Michigan. 



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