ANNELIDS FROM THE N.E. PACIFIC, 24.5 
Note on the Morphology of Micronereis, as @ supposed 
Representative of the Ancestral Type of the Nereida. 
In order to gain a satisfactory idea of the relationship of 
Micronereis to the rest of the family Nereide, a proper under- 
standing of the external structure of the head and its appen- 
dages is, among other things, necessary. As these have not 
been very clearly or fully described by previous workers, I have 
taken some trouble to determine their relations in the Puget 
Sound specimens. Owing to the small size of the animals and 
the crowded condition of their appendages, this was a matter of 
some difficulty. Specimens were examined microscopically, both 
by reflected light and, after clearing, by transmitted light, and 
serial transverse sections of the anterior region of one were also 
eut with the microtome. The following description is based on 
an examination by these methods. 
Text-figure 2. 
Micronereis variegata, Puget Sound. 
Anterior extremity from below, showing peristomial cirri and first 
five pairs of parapodia. X 45. 
The first two setigerous segments bear parapodia consisting of 
one lobe only (text-fig. 2) corresponding to the neuropodium 
of the remaining feet. Anterior to these only one region 1s 
distinguishable, viz., the cephalic or peristomial region, which 
bears the two pairs of eyes on its dorsal surface. On each side 
this region bears also two rounded knobs or humps, anterior and 
posterior (the posterior being also situated rather higher on the 
side of the head than the anterior). Each of these four knobs 
bears two large subulate cirri, one dorsal, the other ventral. 
The points of especial significance are :-— 
(a) There is no trace of palps or tentacles. 
(b) No separate prostomial lobe, as distinct from the peri- 
stomium, is developed. The eyes are situated on the 
dorsal surface of the head in the same transverse plane 
as the peristomial cirri. 
ie 
