NEPHTHYS HOMBEEGIL 21 



Posteriorly the lamellae, branchiae, and cirri diminish, and the gap between the 

 dorsal and ventral divisions is greater. The bristles, however, retain their characteristic 

 features. 



Occasionally a specimen, e. g. from Bressay Sound, shows the lower lobe of the foot 

 somewhat like that of N. caeca, but the dorsal lobe and the structure of the bristles 

 enable ready diagnosis to be made. A similar condition is observed in examples from 

 Denmark. 



Many years ago a series common in the Outer Hebrides and elsewhere had been 

 separated from N~. Hombergii by the fact that the ventral lamella in the anterior third was 

 much less than in the typical form, and both lamellae posteriorly decreased more 

 decidedly. The process at the base of the branchia is also longer (Plate LXVI, fig. 5 

 anterior and fig. 6 posterior foot). Extended examination, however, shows this to be 

 a younger stage in the growth of K Hombergii, intermediate forms leading from the one 

 to the other, and it may be called variety hersivalensis. The chief distinction is that in 

 the variety hersivalensis the ventral lamella in the anterior third is much less than in 

 the type, and both lamellae posteriorly decrease more decidedly. 



Such distinctions, however, may be sexual. The capillary bristles of the variety 

 (Plate LXXVII, figs. 4 and 5) show a somewhat more marked curve. 



Reproduction. — Specimens under two inches in length from the west Voe of Burra, 

 Scalloway, in July, had eggs far advanced and floating freely in the perivisceral 

 chamber. 



Claparede (1868) mentions that the ova are red, as indeed was shown by Delle 

 Chiaje. 



Claparede and Mecznikow 1 describe the telotrochous larva of this species at Naples. 

 The youngest stage is monotrochous with a whip of cilia in front and a ring behind the 

 mouth, in front of which is a pale reddish pigment-band. The alimentary canal has 

 mouth, pharyngeal region, stomach (with greenish pigment), and intestine terminating in 

 an anus at the posterior end and ciliated throughout. A pair of red eyes is present in 

 the larval prostomium in which the greater part of the alimentary apparatus lies. The 

 monotrochous becomes a telotrochous larva by the appearance of rings behind that at the 

 mouth, and the development of the anal ciliated ring. The lateral rings by-and-by 

 develop bristles, the alimentary canal becomes elongated as in the figures of the British 

 examples, and a form like the Naveda-l&rva of A. Agassiz and others is found. Such 

 young forms are remarkable for the greenish or bluish colour of the stomachal region of 

 the gut, whilst in the pharyngeal two teeth appear. Their oldest form had seven pairs of 

 feet with bristles. The authors probably procured these larvae at Naples in November or 

 early in December. 



Var. vasculosa. 



Fine examples of Nejphthys Hombergii were forwarded from Montrose Bay by the 

 late Dr. Howden in 1870. The same year it was dredged in 25 fathoms in Bono Bay by 

 the < Porcupine.' The head agrees with the typical form. The feet (Plate LXVI, figs. 

 1 ' Zeitschr. f. w. Zool./ Bd. xix, p. 25 (sep. abdr.), taf. xiv, figs. 3, 3a— 3d, 1868. 



