152 NERINE CIKRATULTTS. 



occurred in the reproduced segments. The young hooks, as might have been anticipated, 

 showed the main fang and the spike on the crown clearly, indicating that it is friction 

 which renders these minute characters indistinct in this region in ordinary examples. 



Reproduction. — A series of eggs and larvae which appear to belong to this species are 

 figured in Plate XCIV, figs. 4 — 6 and 12. The early egg (fig. 4) shows little that is 

 definite, but by-and-by (fig. 5) the characteristic pear-shape is assumed, with the spiked 

 surface (fig. 5) which the larva also retains (fig. 6) after the appearance of the proto- 

 troch. The egg shown in Plate XCIV, fig. 7, is that of a Nerine — it may be one of the 

 earlier stages of the same species as the foregoing. 



Claparede and Mecznikow (1868) describe two larval stages of this species, and they 

 identify the Sars-Loven larva of Busch therewith. The earlier stage is pyriform, with 

 finely reticulated integument, two eyes, mouth, two sets of provisional spinous bristles, 

 proto- and telotroch. In the later stage the pointed snout has four eyes in a transverse 

 series, short tentacles, a body with numerous segments, the first eighteen having pro- 

 visional spinous bristles longest anteriorly, the rest with ordinary bristles. Bach segment 

 has a branchia or a cirrus. In the rudimentary branchiae they found bacilli (Stabken- 

 follikel). The larva is gastrotrochous, and with a ring of long cilia posteriorly. Such 

 forms are common off the eastern shores of Scotland, probably along with the larvae of 

 Nerine foliosa. 1 Busch and Leuckart also show larvae probably of this species. 



Claparede (1868) alludes to the vascular rete in the snout and buccal segment, and 

 to the structure of the ova with papillae on the outer layer (his chorion). 



Lo Bianco (1909) fixes the period of sexual maturity of this species at Naples, 

 where it is termed " Bsca e ponte che corne," as from February to June, the larvae being 

 found throughout this period. 



Mesnil describes the ripe males as whitish, the females as of a darker green than 

 usual, and eggs and sperms as occurring from the thirty-fifth setigerous segment backward. 

 The eggs are laid at the end of May. He also mentions a young form of fifty-two 

 bristled segments, in which the hooks appeared dorsally on the twenty-first and 

 ventrally on the fortieth segment. In this example the dorsal lamella had a free, pointed 

 upper part, and the hooks had sharper fangs, and he figures them with bifid crowns (in 

 front view). Mesnil found in June larvae of sixteen to twenty- five bristled segments. 

 The snout is sharper than in the adult, and there are two pairs of eyes. The tentacles 

 have a double row of what he terms bacilliparous corpuscles. The first setigerous 

 segment bears a small number of bristles. After the second the feet are quite visible, 

 and the dorsal lamella becomes pointed, the ventral being always rounded. The winged 

 hooks occur ventrally on the sixteenth segment, dorsally on the nineteenth or twentieth. 

 The body posteriorly has the pre-anal circle, whilst the anal appendage has the form of a 

 sucker. The digestive tube gives the larva its special colour, viz. chocolate-brown in the 

 buccal and the first body-segments, bright green in the second and third segments, 

 colourless in the fourth, in the fifth and succeeding segments deep green (vert tres fonce). 



Mesnil 2 gives with considerable minuteness the development of this form, which, at 



1 Such forms may be contrasted with the Sabellarian larva in Plate XCIV, fig. 11. Prof. Caullery 

 has recently given an excellent account of Sabellarian larvaa and the differences between them and 

 the Spionids. 'Bull. Soc. Zool. France/ t. xxxix, p. 168 (1914). 



2 'Bull. sc. Fr. Belg./ t. xxix, p. 132, et seq. 



