152 FRANK R. LILLIE AND E. E. JUST. 



of tests was also made with various dilutions of sea-water super- 

 saturated with CO 2 , all to no effect. 1 In the next place it is not 

 due to any substance common to the females of marine animals. 

 Tests were made with sea-water charged in one case with the 

 emanations of Fundulus, in another case with the emanations of 

 another polychaete, Chcetopterus. Males placed in portions of 

 such charged sea-water gave no reaction whatever, but the same 

 males placed in a portion of sea-water that had contained a 

 female Nereis over night immediately shed sperm abundantly. 

 The mature males of Nereis limbata will not react even to the 

 ripe pelagic females of a nearly related form (TV. megalops). 



It is therefore probable that the substance in question is 

 specific. In this there is involved no new biological principle. 

 It is well known that the males of certain butterflies, for instance, 

 are attracted even from long distances to the females by virtue 

 of some air-borne emanation that is certainly specific. And the 

 same principle must also be involved in the relations of males 

 and females in many other instances. 



Another property of the exciting substance is its lability. 

 This is show r n by its disappearance on standing in the course of 

 about three days, and by its destruction by heat. As regards 

 the first point, the following experiment may be noted: June 24, 

 1911. Four samples of sea- water charged by Nereis females were 

 tested, each of which had been effective when fresh: a was 7 days 

 old, b 5 days, c 3 days, d was fresh. Of these only d was effective 

 in causing male Nereis to shed sperm. Each of the samples a, 

 b, and c, had been tested previously at intervals and each was 

 found gradually to lose its stimulating power in the course of 

 about 3 days. As regards the heat-lability of the substance in 

 question, a series of experiments have shown that it requires 

 about 10 minutes boiling to destroy the power of an -effective 

 solution entirely. Five minutes boiling diminishes the effect 

 considerably. The ineffectiveness after boiling is not due to the 

 removal of oxygen, for it is impossible to restore its effectiveness 

 by aerating. 



The stimulating substance is either neutralized by the presence 

 of sperm in the water owing to combination with some sperm 



1 See footnote, p. 150. 



