274 
PACIFIC SCIENCE, Vol. XV, April 1961 
the male. Sexual dimorphism is unknown for 
M. halei and M. eniwetokensis. 
The large anterior eyes (Fig. 3) on one in- 
dividual of M. eniwetokensis are an unusual 
variation for the members of the genus. The 
appearance of secondary sex characteristics, such 
as enlargement of the eyes prior to sexual ma- 
turity, is widespread in the family Nereidae 
(Reish, 1957), but it is unknown for the 
genus Micronereis (Berkeley and Berkeley, 1953; 
Rullier, 1954). No other morphological differ- 
ences were noted in this specimen collected from 
94 ft. of water in the lagoon. 
M. eniwetokensis comes closest to M. varie- 
Eniwetok Atoll 
5 Statute Miles 
i J 
Fig. 1. Map of Eniwetok Atoll, Marshall Islands. Collections were made at the named islands. Micronereis 
eniwetokensis was collected from the areas indicated by the dots. 
