340 NEREIS (NEREILEPAS) FUCATA. 



curved at the tip as in the next series (heterogomph), sometimes two or three. The 

 inferior group presents bristles with somewhat shorter tapering and spinous tips superiorly 

 (Plate LXXXI, fig. 8 a), then a few having medium tips with a very slight curve, and 

 inferiorly those with shorter tips with a curved probe-point (Plate LXXXI, fig. 8 b). 



The double bristle-tuft appears in the third foot as in allied forms. At the tenth 

 foot (Plate LXXIII, fig. 3 a) the outline trends from above downward and inward. The 

 dorsal cirrus is long and slender, stretching far beyond the tip of the conical superior lobe. 

 The superior setigerous lobe is represented only by the bristles. The lobe beneath it is 

 irregularly conical and considerably less than the superior. The inferior setigerous lobe 

 is bifid and has two strong fascicles of bristles. The ventral lobe is less than either of 

 the preceding and conical at the tip. The ventral cirrus does not reach the extremity of 

 the latter. The bristles of the superior lobe have long tapering tips; those of the inferior 

 are in two groups — the upper having bristles with long tips above and with short tips 

 below. The inferior group has only those with short tips (epitokous female). 



Towards the enlarged end of the shaft the camerated region of the bristles is 

 narrowed, and the markings are less regular. At the base of the shaft the cameras become 

 indistinct, and the diameter of the bristle is less. The spines are rather brittle. At the 

 base they are pellucid, then brownish, and finally black distally. The inferior spine is 

 the stronger. 



Reproduction. — Two females having the body distended with ova of moderate size 

 came from deep water off St. Andrews Bay in January (E. M.). Others with large ova 

 were tossed on shore after storms the same month. One in March had smaller ova. In 

 October the reproductive elements are but slightly developed. Prof. Garstang 1 and 

 Dr. Allen give May as the breeding season at Plymouth ; whereas Lo Bianco has found 

 mature forms in October and November as well as from April to July. In the ripe 

 condition the ova extend forward to the anterior region ; whilst the coloration of the 

 posterior end of the body in some is lost by the prominence of the internal mass of 

 greyish ova (De St. Joseph). 



In an incipient epitokous female from Cornwall, kindly sent by the late Dr. Baird, a 

 slight enlargement is observed at the inner border of the ventral cirrus of the twenty- 

 first foot. This increases at the thirtieth to form a small lamella adherent to the inner 

 border of the cirrus. This lamella continues to the sixtieth and again diminishes, 

 disappearing about the seventieth foot. In the same way a slight enlargement appears at 

 the inner border of the base of the dorsal cirrus about the twenty-sixth or twenty- seventh 

 foot. Behind this it by-and-by forms an elevated crest, and continues to the same 

 region as the former. Coincident with these a small lamella occupies the posterior surface 

 of the inferior setigerous process, its margin in lateral view being visible above and below 

 the lobe, but very little of it is seen at its tip. Traces of this continue beyond the 

 seventieth foot, and then disappear. The bristles retain the normal form in this specimen, 

 no swimming bristles being present. The ova are ripe or nearly so. 



In an epitokous female the dorsal lobe of the foot gradually increases in size after 

 the tenth, until at the twenty-seventh (Plate LXXIII, fig. 3 6) the upper region of the 

 foot, including that between the dorsal cirrus and the body and the dorsal lobe, forms a 



1 ' Journ. M. B. A./ vol. iii, p. 225. 



