306 NEREIS DUMERILII. 



The ventral lobe is bluntly ovate and the small ventral cirrus does not extend so far 

 outward as its tip. 



At the thirty-seventh foot (Plate LXXII, fig. 4 b) a considerable increase in length 

 has occurred, both by the elongation of the region between the body and the dorsal cirrus, 

 and the elongation of the lobes themselves. The dorsal cirrus is still long, and has two 

 opaque glandular masses near its base. The dorsal lobe forms a long triangle, and the 

 superior setigerous lobe is indicated by two small papillas in the sulcus. The next lobe is 

 nearly lanceolate, though there is an elevation on its ventral border near the base. The 

 inferior setigerous lobe forms a truncated cone (though in the larger specimens a longer, 

 pointed papilla and a shorter are present) bearing bristles with tapering tips 

 superiorly and those with short tips inferiorly. The ventral lobe is tongue-shaped, and 

 the ventral cirrus small, only reaching to the middle of the lobe above it. 



The general size of the foot is diminished at the fifty-seventh (Plate LXXII, fig. 4c). 

 The dorsal border is convex and is entirely occupied by the opaque granular bodies now 

 in close apposition. The dorsal lobe does not differ much from the condition in the 

 thirty-seventh foot, forming a long, lanceolate process. The superior setigerous lobe has 

 at least one prominent papilla. The next lobe is elongate-lanceolate as in the thirty- 

 seventh foot, only the inferior elevation is less. The inferior setigerous process is conical 

 with a long and a short papilla, the latter for the spine. The ventral lobe is tongue-shaped, 

 and the cirrus is somewhat longer than in front. The upper bristles with short tips are 

 considerably stronger than those beneath them. 



At the seventy-seventh foot the lobes, especially the two upper, are larger in propor- 

 tion. The opaque granular bodies have fused into one great mass which encroaches on 

 the base of the dorsal lobe. The other parts of the foot are similar to the fifty-seventh. 

 The upper bristles with short tips in the inferior setigerous lobe remain stronger than 

 those beneath, as if in this region of the body they had a special function— probably in 

 connection with the tubicular habits of the species. A slight indication of a wing is 

 observed beneath the hook in the form of a double line at the margin. 



In the epitokous form (Iphinereis fucicola) the feet are furnished with long, 

 translucent swimming bristles (Plate LXXXI, fig. 4 b) the terminal piece of which is thin 

 and flat like the blade of a scalpel. The serrations on the edge (figured by Ehlers) were 

 not definitely made out in these examples (long preserved). The shaft is equally 

 translucent, and differs from that in the ordinary condition in having two stripes with the 

 transverse bars or cameras in the centre. Those bristles with short tips occurring in the 

 epitokous forms are exemplified in Plate LXXXI, fig. 4 c, from the tenth foot. The 

 head in these (Plate LX, fig. 10 6) has remarkably large eyes and long tentacular cirri, 

 which in spirit show slight crenations. 



The epitokous forms occur most plentifully in the warmer months, e.g., in June. 

 Their rounded heads, and large, often connate, eyes, which severally have lenses, are 

 characteristic. 



In a male heteronereid (Plate LX, fig. 10 c) the first fifteen feet (the average 

 number) are little modified, except the dorsal cirri anteriorly. The head is short and 

 rounded, the large eyes occupying the lateral regions and apparently having vision 

 dorsally, laterally, and anteriorly. The softness and delicacy of the tissues, as pointed 



