360 EVARNE HUBREOHTI. 



hook being present. All are very translucent and delicate. One of the elongated forms 

 near the dorsal edge of the fascicle is shown in Plate XXXIX, fig. 25, and a more highly 

 magnified tip in Fig. 27, the arrangement of the spines and the short bifid tip being 

 characteristic. The bristles from the middle of the foot are exceedingly translucent and 

 very faintly serrated (Plate XXXIX, fig. 26, and a tip more highly magnified in Plate 

 XXXIX, fig. 28). In large examples from Norway the dorsal bristles show more 

 acutely-tapered tips, but otherwise the characters closely approximate. 



The dorsal cirri have a filiform tip without enlargement, and rather long clavate 

 papilla3 sparsely distributed. The ventral cirrus is slender and elongate with a finely 

 tapered tip, which in the preparations ends in a slight enlargement. Short clavate 

 papillas — sparsely distributed — occur on the surface. The tip reaches considerably 

 beyond the base of the lowest bristles. 



The species is broadly distinguished from E. impar by the deep brownish hue of the 

 dorsum and the brownish-purple proboscis, by the structure of the scales, which have 

 only large horny papillse and few and slender cilia, by the longer, more delicate, and less 

 tapered dorsal bristles with shorter tips, and by the more slender ventral bristles with 

 much more finely tapered tips. 



The capture of a variety during the ' Porcupine' Expedition of 1870 at 690 fathoms, 

 in which the eyes are large — especially the anterior pair, which have a lens-like corneal 

 thickening — and still more the presence in Norwegian waters of a form closely resembling 

 Evarne Johnstoni in colour, but differing in having very large eyes and in other minute 

 particulars, raise the question as to how far such species vary with age, sexual con- 

 ditions, and environment. The younger Norwegian forms agree with the description of 

 E. Johnstoni, except that some have larger eyes (without a lens-like thickening). In the 

 larger and older forms, however, the eyes still further increase in size, the lens-like corneal 

 thickening of the anterior pair leaving only a rim of black pigment round the edge. The 

 posterior pair are also provided with the central lens-like thickening. The dorsal bristles 

 are broader, more acutely pointed, as well as somewhat more closely spinous ; and the 

 smooth portion at the tip is longer, so that it is dagger-shaped. In the ventral bristles 

 the tips are bifid even to the ventral edge of the foot. Age, therefore, considerably 

 alters the foregoing organs. The scales differ from those of E. impar, and agree with 

 those of E. Johnstoni. 



The prominent question therefore is, can Evarne impar pass insensibly — by epigamy, 

 for instance — into E. Johnstoni, as in many other groups of annelids ? So far as present 

 observations go, a negative reply would seem to be most in harmony with the structure 

 of the scales, the eyes, bristles, and the geographical range. Further knowledge may 

 show the propriety of union, but at present it is better to leave the question as it is. 



Prof. Giard (1886) finds a third and closely allied species of Evarne commensalistic 

 on Cucumaria pentactes off Brittany and the neighbouring shores of France. 



3. Evarne Hubrechti, 1 Mcintosh, n. s. 

 Specific Characters. — Head comparatively small, and in the adult the eyes are very 

 large; both pairs more or less lateral in position. Median tentacle long, tapering, 

 1 Named after the distinguished Professor of Zoology at Utrecht. 



