2O6 E. E. JUST. 



Nereis. This is strikingly brought out by a study of the tables 

 especially when one recalls that I gave attention wholly to 

 Platynereis for the year 1913. Curves of the runs of Platynereis 

 would show that the heights tend to fall in with those of Nereis. 

 The lunar periodicity is therefore more like that of Nereis limbata 

 than that of N. dumerilii which in some respects Platynereis 

 resembles. 



II. EGG-LAYING. 



Males and females caught with a hand-net in the evening at 

 the surface of the water and kept in separate dishes may be 

 studied in the laboratory. If a male be transferred with a 

 female to a dish of clean sea-water, the phenomena observed in 

 the sea may be readily followed. The female packed eggs 

 discernible through her pale thin body wall swims slowly in a 

 straight line; or, with head bent at right angles to the body 

 describes a circle of which the head is the center. The male 

 swims in spirals tangential to the surface of the water. Soon his 

 spirals are along the course of the female, her body finally 

 becoming the long axis of his helical body. He entwines the 

 female through this performance and straightens out, thus 

 clutching her in the twist of his body. If this embrace be in the 

 posterior region of the female's body, the male loosens slightly 

 and pulls himself along the female's body. The task appears to 

 be exacting. Often I have observed a rather small male that 

 had worked himself forward after having grasped an unusually 

 large female near the anal segment fall apparently too exhausted 

 to complete the courtship. As the male slips along forward over 

 the female, he lashes his tail back and forth. The female bends 

 her head as if seeking the tail. If the female keep her body in a 

 straight line, the male must move anteriorly until he entwines 

 her body in the pharyngeal region. He now forms a coil around 

 her head of which his tail is the apex. He thrusts his tail down 

 into the coil of his own body and so into the waiting jaws of the 

 female. The female is quiescent throughout. About six seconds 

 after the female has received the anal segment of the male, the 

 animals separate and eggs stream from the posterior segments 

 of the female. The male may be held for a time by the female; 

 if so he swims around, dragging her. I believe that the eggs 



