258 



NEREKLE. 



Dendronereis from Mozambique and the Philippines, in which the ramifications of the 

 dorsal cirrus are alone diagnostic. In his specific characters he makes use of the number 

 of the different bristles in each division of the foot, a method that has not been followed 

 here. Of the genus Nereis he makes four sub-genera, viz., (1) those in which all the eight 

 groups of paragnathi are present (Neanihes, Kinberg) ; (2) those in which one or more 

 groups are absent (Nereis s. st. Kinberg), whilst the third and fourth sub-genera have the 

 paragnathi only on one ring, — Geratonereis, Kinberg, having them on the maxillary, and 

 Eunereis, Malmgren, having them only on the basal ring. 



For the British species of Nereis it is unnecessary to make a special classification. 

 The main lines of previous efforts have been indicated in the foregoing summary, and 

 that of Ehlers, for instance (p. 255), will suffice for reference. The structure of the 

 body-wall throughout the series presents no basis for differentiation, so that characters 

 derived from the armature of the proboscis, the structure of the feet, and other points, are 

 alone available. Moreover it is doubtful how far the presence of a continuous bar of 

 chitin in Group VI should be relied on as a satisfactory distinctive character, the two 

 British forms which fall under this head being Nereis (Perinereis) Marionii and Nereis 

 cuUrifera. Little is gained by its adoption, since otherwise there are no bonds of note. 

 Then, again, the British forms with a complete series of paragnathi from I to VIII are 

 N. cuUrifera and A T . virens, yet in other respects there is no special connection. Neither 

 is the absence or scanty presence of paragnathi, as in Nereis longissima, followed by other 

 special characters, though the condition is interesting (e.g. in the foreign Lycastis). All 

 the British forms have distinctly biramous feet, that is, a dorsal and a ventral division, 

 no example of Lycastis having yet been procured on our shores, though a persevering 

 search on the southern coasts might be successful. 



In his researches on the eyes of Annelids, Andrews 1 (1892) regards the whole eye as 

 epidermal, and he gives figures of the minute structure in Nereis, showing that behind 

 the lens is a central axis with its sheath followed by blue pigment, then yellow pigment 

 in the central nerve-axis with its nucleus, and nerve-processes posteriorly. 



Various allusions are made to the development of Nereids, and amongst others the 

 youngest larva3 mentioned by Milne Edwards 2 (1845) had three complete segments and a 

 fourth developing, two anterior cirri, two tentacular cirri, and two anal cirri. 



Busch 3 (1851) describes a free-swimming larva of Nereis with six bristled segments, 

 two sub-tentacles, two anal cirri, and four eye-specks. 



Wilson 4 (1892) describes a monotrochous larva of Nereis limbata, which exhibited 

 marked heliotropism. In the following stage on the twelfth clay it is still pelagic, but is 

 less active. 



Goette 5 gives an account of a small prototroch of Nereis, and Salensky 6 alludes to 

 the pelagic stages of Nereis Dwnerilii with three pairs of feet and a pair of eye-specks. 

 He also describes the ninth day larva of Nereis cuUrifera as having three pairs of feet 

 with bristles, two frontal cirri, two tentacular cirri, and two anal cirri. 



1 ' Journ. Morphol./ 1892. 



2 ' Recherches/ p. 167, Taf. x and xi. 



3 'Beobacht./ p. 69, Taf. ix, fig. 11. 



4 ' Cell Lin./ 1892, p. 120, figs. 82 and 91 



5 'Unters./ 1882, p. 84, Taf. vi, fig. 19. 



6 < Stud/ ii, 1882, Taf. xxiv, fig. 10 n. 



