EUNICIDiE. 343 



Hornel (1891) states that the worm takes possession of the shell of the mollusk first, 

 and that it tolerates the intrusion of the hermit-crab for benefits subsequently received. 

 This is uncertain. It is more probable that the same affinity as in other commensalistic 

 forms holds. 



De St. Joseph (1898) considered Wiren's view that the posterior region of the body 

 was furnished with thinner longitudinal muscles to fit it for its peculiar habitat was 

 untenable, and that such was only a step to the Heteronereid condition. 



At Naples Lo Bianco 1 (1909) finds that this species especially frequents Prosobranchs 

 inhabited by Eupagurus Prideauxii. 



Family XI. — EuNiciniE. 



Head somewhat triangular or semi-oval, with lobate palpi more or less united, rarely 

 lateral tentacles, or none. Tentacles subulate or elongate posteriorly; sometimes none. 

 Eyes two or four or absent. Nuchal organs in the form of ciliated grooves (Bacovitza). 

 Body long, vermiform, often slender, somewhat rounded, iridescent, with numerous short 

 segments, ending in two or four anal cirri. Peristomial segment bi-annular, with two 

 tentacular (nuchal) cirri or none. The body-wall is characterized by its great muscu- 

 larity, and the nerve-cords are comparatively large, and lie in the interval between the 

 ventral attachments of the oblique muscles. Externally are the basement-tissue, the 

 hypoderm, and the cuticle. The changes made by the ripe sexual elements in the male 

 are indicated in Fig. 76. Proboscis with paired or unpaired horny or calcareous plates; 

 one superior maxilla with hooked tip on each side, simple or toothed ; great dental 

 plates hooked anteriorly, toothed, truncate or convex, besides smaller anterior and lateral 

 plates. Mandibles 2 chisel-shaped. Feet simple or double, bearing dorsal (often with 

 bristles) and ventral cirri, one or more spines, and one or two fascicles of bristles ; often 

 without cirri, but with a setigerous lobe. Bristles simple or simple and compound ; the 

 former sometimes slender, winged, the latter with hooked tips. Uncinate spines 

 posteriorly. 



Branchia3 springing from the dorsal cirrus in the form of simple styles or pectiniform 

 or sub-fascicular, and occasionally as spiral tufts, or absent. Blood has haemoglobin. 3 



Goodrich states that the segmental organs are always provided in the adult with 

 large funnels opening into the coelom, and they perform the function both of excretory 

 and genital ducts. They were misunderstood by the earlier observers, such as Ehlers. 

 Fage 4 considers they have a close analogy with those of the Syllidae, though they differ 



1 The recent loss of this able observer at the Naples Zoological Station must be deplored not 

 only by the staff, but by every marine zoologist. 



2 In the figure in the ' Cambridge Nat. Hist/ (p. 270, fig. 140, l) these organs appear to have 

 been inverted. 



s Ray Lankester, c Proc. Roy. Soc./ No. 140, p. 2, 1873. 



4 < Ann. Sc. Nat./ 9 e ser., pp. 347—352, figs. 36 and 37, pi. vii, f. 32—36. 



