332 NEREIS (ALITTA) VIRENS. 



aperture which has a lax, fringed border, except interiorly, where a smooth portion gives 

 origin to two long cirri. Each of the latter has a dark basal region of a brownish-purple 

 hue on the ventral surface, and is thus distinguished from the adjoining parts. 

 Peristomial segment about twice the breadth of the succeeding. The colour of the dorsum 

 is of various shades of iridescent bluish-purple, the same tint extending to the shorter 

 anterior feet. The finest specimens have the great lamellae coloured greenish-purple. 

 Others vary according to the prevailing tint of the specimen. The lamellae are also finely 

 tinted and iridescent, and as they gracefully fold over each other like the slates on a roof 

 the effect is striking. The dorsal cirrus, which is larger anteriorly than in the feet with 

 foliaceous lamellae, is of a deep green. The ventral surface is pale iridescent pinkish, 

 becoming deeper posteriorly, and with a pinkish belt across the front of each segment. 

 In others this surface is iridescent bluish, with the belts at the anterior part of each 

 segment of a deeper hue. In contraction the tints are darker. 



Ehlers (1868) observes that in the atokous form the vent has inferiorly two long cirri, 

 whereas in the epitokous form the vent has a ring of short papillae. 



The proboscis (Plate LXI, figs. 2 and 2 a) in extrusion is greyish-blue, somewhat 

 lighter than the hue of the body, and similarly iridescent. Dorsally, in front of the palpi, 

 and on the basal ring, one or two paragnathi (VI) occur on the eminence on each side, 

 with an intermediate point (V), whilst on the maxillary (distal) segment a group (II) — 

 somewhat triangular in outline and with the apex in front — lies on each side behind the 

 jaws, with two points (I) longitudinally arranged between them. Ventrally (Plate LXI, 

 fig. 2 a) the basal segment has a somewhat irregular double row (VII and VIII) of 

 paragnathi on the folds, and they leave but a brief interval between them and the dorsal 

 points in front of the palpi. On the maxillary segment a long, somewhat irregular double 

 row (IV) proceeds backward as a longitudinal band from each jaw, and in the middle is 

 a transverse belt of points (III), the larger in a single row behind, and the smaller dotted 

 in front. The maxillae have six teeth. The smaller examples between tide-marks have, as 

 a rule, the paragnathi more complete than the large epitokous forms stranded on the beach. 



From the posterior part of the pharynx pass two elongated caeca, which have 

 internally a coating of blackish pigment-granules, the smaller showing active molecular 

 motion when separated. The walls of the caeca are tough, and longitudinally plaited. 



The coelomic bodies are transparent structures of an elliptical form, the longer 

 diameter having an average of T1 f 5 - - of an inch (O02 mm.), many being much shorter and a 

 few longer and larger. Their transverse diameter also varies (Plate LXI, fig. 3). Most of 

 these bodies are faintly striated longitudinally, and similar markings occur in the circular 

 corpuscles. They are protoplasmic, and yield when they encounter obstacles. 



Circulation. —The blood must be in considerable quantity in large specimens. 



The ultimate fibrils of the ventral muscle presented peculiar fibrillation as if from 

 fine lines crossing each other obliquely. In the centre of the fibril is a granular streak, 

 though in some this could not be made out. Acetic acid and calcium chloride obliterated 

 the streak. A contracted fibril is seen in Plate LXI, fig. 4. Occasionally the streak in 

 the fibril assumes the form of a granular band (Plate LXI, fig. 5), the central region 

 representing the contracted fibril, and the transparent sarcolemma or other muscular 

 element projects externally. 



