BREEDING HABITS OF THE HETERONEREIS FORM 



OF PLATYNEREIS MEGALOPS AT 



WOODS HOLE, MASS. 



E. E. JUST. 



Verrill ('73) first described Platynereis megalops figuring in his 

 "Report" a male of the heteronereid phase. Later ('79) he 

 figured the nereis-form and the female of the heteronereis-form 

 changing the name he first gave, Nectonereis megalops, to Nereis 

 megalops. Andrews, who ('91) had discovered the egg Nereis 

 limbata, in a paper on the eyes of annelids speaks of the worm as 

 Nereis alacris. I am indebted to Dr. J. Percy Moore who iden- 

 tified the animal as Platynereis megalops, Verrill. The belief 

 seems to prevail that in the study of the cell lineage of Nereis 

 ('92) Wilson indiscriminately used the males and females of 

 Nereis and Platynereis. But this belief is by no means founded 

 on any statement in Wilson's paper. Bonnevie ('08) has 

 perhaps strengthened popular misconception through her descrip- 

 tions of the "two varieties" of Nereis limbata at Woods Hole. 



I. SWARMING HABITS. 



The swarming of Platynereis is closely similar to that of Nereis 

 (cf . Lillie and Just) . There seems to be some variations as noted 

 below. The behavior shows as that of many other forms a 

 definite lunar periodicity : the sea-urchins (Tennent), the Japanese 

 palolo (Izuka), the Pacific palolo (Woodworth and others), the 

 Atlantic palolo (Mayer), Amphitrite (Scott), Nereis dumerilii 

 (Hempelmann), etc. 



Observations were made during the seasons of 1911, 1912 and 

 1913 at the Marine Biological Laboratory, Woods Hole, Mass. 

 The swarming habits of Platynereis have not been worked out 

 as fully as have been those of Nereis limbata (Lillie and Just, '13). 

 In the first place during 1911 and 1912 attention was focused 

 mainly on the swarming habits of Nereis; moreover, at all 

 times the primary object in the collecting of Platynereis was for 



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