NEREIS PELAGIOA. 277 



The Johns tonia prolifera of De Quatrefages 1 is a Heteronereis of this or other species 

 of Nereis. An epitokous example of this form is in all probability the Nereis bipinnata of 

 Montagu (MS. Drawings, Linn. Soc., Plate XXIX, fig. 3, 1808). 



Female Heteronereid. — In September the feet of the female become very vascular, 

 so as to give a deep red appearance to the sides (Plate LII, fig. 1), and as the tips of 

 the lobes of the feet are pale, the aspect is the more striking. The perivisceral cavity 

 is loaded with eggs which have one large oil globule. They are opaque whitish, and the 

 majority are of equal size. There is as yet no indication of structural change in the feet 

 or other organs. 



At the beginning of February large females show a somewhat deeper and beautifully 

 iridescent russet-brown of the body, probably from the tint of the eggs, which are faint 

 salmon or buff coloured in mass. The head and tentacles are of the same greenish hue as 

 the males, the palpi having the tips dull brownish-orange like the proboscis. The same 

 whitish patch (though less developed) occurs behind, between and in front of the eyes. 

 The latter are not enlarged. The armature of the proboscis is typical. The feet show 

 no evident change in front and apparently not much posteriorly, their extremities being 

 pale. The ova are of comparatively large size. The Nereis ferruginosa of Montagu 

 (MS. Drawings, Linn. Soc, Plate LII, fig. 2) may represent this stage, and it appears to 

 be the Nereis fulgens of Dalyell. 



Before the heteronereid condition is developed, the female Nereis pelagica is thus 

 distinguished by the lustrous deep brownish or bronzed colour just mentioned, and the 

 size is frequently larger than that of the male. As the ova develop and distend the 

 posterior region the latter assumes a somewhat pale hue, and by-and-by also the body 

 generally becomes somewhat shorter and broader from contraction. The change of colour 

 does not at first much affect the general aspect, and no sign of alteration in the structure 

 of the feet is visible externally, but they are highly vascular, the dorsal edge of each 

 being connected with the body by a reticulated bar of blood-vessels. The eggs at this 

 stage are dull yellowish and minutely granular, and have none of the large globules of a 

 subsequent stage; moreover, in the lustrous brown condition of the adult they are more 

 minute. The eyes as yet show no perceptible change. 



The next stage is characterized by the lustrous pale-greenish condition of the body 

 from the twentieth foot backward, whilst the brownish-olive hue remains in front. The 

 head has a pale trifid mark between the eyes, the median spur going forward. The eyes 

 do not show marked alteration, but the anterior dorsal cirri have a slight enlargement at 

 the base. The pale region is loaded with greenish -white ova measuring -^ mm. The 

 vascularity of the feet is pronounced. 



Then the deep brownish or olive colour anteriorly gives way to a paler greenish 

 brown, the posterior region becoming still more pale as the eyes enlarge. Various isolated 

 and fixed black specks appear, but whether in the gut or body-wall is not clear. The 

 pallor makes the blood-vessels of the feet and of the dorsum conspicuous. The head and 

 anterior region retain in some the brownish hue mingled with green for some time, but 

 the tentacles and tentacular cirri are pale greenish. 



At a further stage (24th February) the anterior region of nineteen segments is olive 

 1 f Ann. Sc. Nat./ 3 e ser., fc. xiv, p. 350, pi. viii, fig. 1, August, 1850. 



