288 NEREIS OULTEIPEEA. 



On the 18th of January the males, which are smaller than the females, have the 

 coelom laden with sperms, which are not very active, though they exhibit slight move- 

 ments. The " head " has a knob followed by a somewhat ovoid region terminating in 

 the filament posteriorly. The under surface of the worm is pale anteriorly, reddish from 

 the blood-vessels posteriorly. 



On 6th December some of the females are laden with ova, which when extruded 

 in mass have a dull or faintly greenish aspect. The ova are surrounded by a coating of 

 yellowish cells filled with refracting granules, a coarser series also filling the ova, 

 which present a large nucleus and nucleolus. On the 18th of January the ova are still 

 numerous in the perivisceral cavity, and the nucleus and nucleolus can be made out 

 under a lens. 



The only Heteronereis pertaining to this species comes from Ireland, the exact 

 locality not being indicated. The specimen, a male, is between two and three inches 

 (two inches in spirit). The eyes are large and convex, the anterior almost touching the 

 posterior on each side. They are chiefly developed laterally, and have a small lens in the 

 centre of each. The pigment of the dorsum of the body seems to have been specially 

 developed in bands and touches across the middle of each segment. The anterior region 

 has nineteen feet — distinguished as usual by their greater thickness. The succeeding 

 region has seventy-two feet, furnished with the swimming bristles and lamella. The 

 last, however, are very small. The vent is everted and richly papillose, and two long 

 cirri project posteriorly. The segments of the anterior region are wider, those of the 

 posterior narrow, but the sulci between the segments are in both transverse. The 

 paragnathi of the proboscis do not appear to differ from the typical form. The first 

 foot has its dorsal cirrus enlarged, as in N. pelagica, and a slight increase has also 

 occurred in the ventral. This enlargement continues to the seventh foot as regards 

 the dorsal cirrus, but it ceases sooner in the ventral. The feet remain of the 

 normal structure till the seventeenth, in which the dorsal cirrus has a papilla at 

 its ventral border near the tip, this marking off the filiform termination, and the 

 ventral cirrus of the same foot presents a swelling near its tip. The dorsal cirri of 

 the eighteenth and nineteenth segments show one or two additional papilla?, and the 

 terminal region is often bent at an angle. The tips of the ventral cirri of the eighteenth 

 and nineteenth are as in the seventeenth, but the nineteenth (Plate LXXI, fig. 8 d) 

 has a small process (lamella) arising on the inner side of the base of the cirrus, and a 

 more minute one to its exterior. A small lamella also appears at the lower edge of the 

 tip of the inferior setigerous process. An opaque granular mass (gland ?) occurs at the 

 base of the dorsal cirrus, and the tips of the five lobes of the foot and the base of the 

 ventral cirrus are all similarly opaque. The bristles of this foot retain the normal outline. 



The heteronereid condition is more distinctly pronounced in the next (twentieth) 

 foot (Plate LXXII, fig. 1), which presents a small vertical lamella internal to the base 

 of the dorsal cirrus. The latter has four papillae and traces of two others below the 

 filiform tip. The inferior setigerous process has a considerable fan-shaped lamella with 

 a pit in the middle at the tip, as if from the coalescence of two folds. The lamellas at the 

 base of the ventral cirrus have increased, and the cirrus comes from the edge. The 

 margins of the second lobe and of the ventral also show traces of increase. A few bristles 

 of the atokous type remain in the superior setigerous lobe, but the ends of the shafts and 



