FRESH-WATER NEREIDS FROM THE PACIFIC COAST AND HAWAII. 219 



tions began to die off when a specific gravity of 1.014 was reached. Eisig gives a 

 careful statement regarding the changes brought about in the worms by the gradual 

 reduction in the salinity of the medium and attributes death to the hacmolytic action 

 of the fresh water, which naturally is much more striking and immediately fatal when 

 the worms are plunged directly into it. In view of the long held and generally accepted 

 theory that the Oligochaeta have sprung from capitellid-like ancestors, the imperfect 

 euryhalinism of Capitella capitata and the recent discovery in the Ouanary River, 

 French Guiana, of a fresh-water capitellid, Eisigella ouanaryensis Gravier (:01), 

 would no doubt be regarded as important evidence in favor of this theory were it 

 not for the numerous euryhaline Nereidse and Sabellidaj. 



As would naturally be anticipated, the Nereidse afford many subjects favorable 

 for experimentation in this direction. N. diversicolor, as already stated, lives in 

 brackish water of very slight salinity, and it will endure transfer to fresh water with- 

 out difficulty (Nusbaum, :01; on the authority of Giard). According to Webster's 

 (79) statement, Nereis culveri of the New Jersey coast is equally euryhaline, although 

 this species is not known to live naturally in fresh water, or apparently even in brackish 

 water of greatly reduced salinity. Yet, according to Webster,* the worms can be 

 put directly into well-water without causing their death or checking the flow of the 

 blood, which he states is the immediate result of subjecting N. limbata to the same 

 experiment. The dwarfish examples of N. virens living in the muddy banks of the 

 Charles River in the vicinity of Boylston Bridge, Cambridge, where the water is 

 decidedly brackish (Hamaker, '98) can also be placed directly in fresh water without 

 checking the circulation, changing the color of the blood, or apparently doing it the 

 slightest injury. I have found it will live for at least a week in ordinary tap water 

 death resulting, apparently, from lack of food. The experiment of transferring 

 littoral specimens of N. virens to fresh water remains to be tried. 



The important experiment of transferring a form not known to be naturally 

 euryhaline, living nowhere in fresh or even in brackish water, but having a 

 near ally that lives exclusively in fresh water, has been tried with Fabricia stellaris 

 Blainville by Dr. Moore, and with perfect success. The change to fresh water is 

 easier for Fabricia than the change to sea-water for Manayunkia. As originally 

 pointed out by Leidy ('59) Fabricia of all marine Sabellids is most nearly allied to 

 Manayunkia. Without doubt both Manayunkia and Dybowscella are offshoots 

 of Fabricia stock. That both Fabricia and Manayunkia, although not exhibiting 

 euryhalinism in their habitats, are in reality both very euryhaline and in nearly 

 equal measure, is possibly as good evidence of their relationship as any afforded by 



* Mr. J. E. Benedict, of the National Museum, kindly called my attention to Nereis culveri. 



