266 NEREIDS. 



the nereid female except that the large eyes are almost coalescent, the colour of the body 

 is dark orange, and from the sixteenth to the fourth in front of the tail swimming 

 bristles are present. The reddish-brown male heteronereid he procured in August, and it 

 measured about 20 mm. and had fifty-seven segments. The head has enormous eyes, 

 whilst the body has three regions. The first region is composed of fifteen segments 

 having bristles resembling those of the nereid form. The first four feet have the 

 peculiar hook-like dorsal cirrus, the first two, as in the nereid, having neither spine nor 

 bristles clorsally. Segments five to eight have the dorsal cirrus spatulate, whilst from 

 nine to sixteen it is short and subulate. The second region consists of thirty segments with 

 swimming bristles on the feet, and the heteronereid lobes are greatly developed, the 

 largest being the foliaceous lobe of the inferior division. The third region comprises 

 eleven segments and is translucent, or, if the sperms are developed, white. The feet 

 resemble those between the ninth and sixteenth, only their lobes are less developed. 

 Moreover, the inferior division has curious brown spines with a crotchet-like tip. The 

 tail resembles that of the nereid form, and the tissues are transparent (De St. Joseph). 



Unfortunately the single preparation of the heteronereid is incomplete, so that only 

 an imperfect account of this form is at present possible. The foregoing remarks, 

 however, will aid in the discrimination of the form, the life-history of which is still in 

 need of investigation. 



SECTION II. 

 NEREIDS WITH SEPARATE HORNY PARAGNATHI. 



The British forms 1 in this group may for convenience be arranged according to the 

 condition of the paragnathi thus : — 



1. All the eight groups of paragnathi present. 



Nereis (Alitta) virens, Sars. With a leaf -like dorsal lamella. Large bluish-green 

 worm, varying in size and occasionally reaching three feet in length. 



2. Group V or V and VI absent. 



Nereis pelagica, L. Marked distinction between proximal and distal rows on 



ventral surface of basal segment. Dorsal cirri longer than feet. Length 



4—8 ins. 

 Nereis (Ilediste) dirersieolnr, 0. F. Midler. Distinguished from N. pelagica by 



the much smaller paragnathi and the broader head ; dorsal cirri not longer 



than feet. 

 Nereis (Praxitliea) Sclimardwi, De Quatrefages. Conspicuous glands in feet; 



feet bluntly lobate in front, but upper lobe much elongated posteriorly. 



Length 4 — 6 ins. 

 Nereis (Leontis) Dumerilii, Aud. & Echv. Paragnathi very minute, closely 



arranged in pectinate rows. Two glands on each foot posteriorly. Very 



long tentacular cirri. Length 2 — 3 ins. 



Nereis (Nereilepas) fucata, Savigny. Dorsal lobe of foot large with the cirrus 



1 Vide a useful key to the British species by Major Elwes, Mourn. M. B. A./ vol. viii, p. 357 

 1909. 



