280 F. M. Turiibull — Anatomy and Habits of Nereis vlrens. 



brancbes to the external or dorsal tentacular cirri ; a, head-ganglion with four 

 eyes ; h, b, nerves to antennae ; c, c, nerves to palpi ; iv, iv, series of ganglia and 

 nerves on the ventral side of proboscis ; /, /, jaws, ventral side ; ?/, y, the series of 

 ganglia and nerves on the dorsal side of the proboscis; / / jaws, dorsal side. 

 In figure 27 the proboscis has been revolved about a line passing through g, g, so 

 that the ventral side is uppermost. The head and abdominal ganglia are in their nat- 

 ural position. The position of figure 28 is reversed so as to show the relations of the 

 dorsal ganglia y, y, to the ventral ganglia w, w (fig. 27). 



Plate XLIV. 



Fig. 20. — Circidation of blood in Nereis virens, and also the alimentary canal in its 

 natural position ; to, mouth ; x, pharyngeal region of proboscis ; p, dental region 

 of proboscis; o, oesophageal region of proboscis; r, intestine, covered with a 

 vascular network, which is connected in each segment with the large dorsal and 

 ventral vessels by short Ijranches ; j, salivary glands ; a, large dorsal vessel ; b. 

 large ventral vessel; c, c', c'', peripheral vessels; d, branches from the dor- 

 sal side of the feet; e, branch to oesophagus ; /, /'', branches to the ventral side 

 of the feet; s, lateral branch, supplying the vascular network {g) and first three 

 lateral appendages; A", vessel from network (g) to base of tentacular cirri; t, 

 branch from the vascular network (u) on the proboscis, to the large ventral vessel 

 (6) ; V, branch from the large dorsal vessel (a), at base of head, to the network (u) 

 on the proboscis. 



Fig. 21. — Diagram, showing the disposition of the large ventral vessel, and its branches 

 on both sides, in the anterior portion of the body ; I, continuation of the large 

 ventral vessel along the median ventral line beneath the muscles of the proboscis ; 

 n, vascular ring surrounding tlie pliaryngeal region of proboscis ; otherwise the 

 lettering is the same as in fig. 20. The arrows indicate the direction in which 

 the blood flows. 



Pig. 22. — Diagram to show the circulation of the blood, and also the relative position 

 of the parts, in one segment of the body ; i, intestine ; p, perivisceral cavit_y ; h, 

 crypt from which aciculee grow ; 1. muscles of crypt, which are attached to the 

 base of the foot ; g, g, segmental organs ; k, walls of body ; n, a ganglion of the 

 abdominal chain; «, large dorsal vessel; b, large ventral vessel; c, peripheral 

 vessel ; /, branch to ventral side of foot ; d, branch from dorsal side of foot. 



Fig. 23. — Circulation of the blood in the last posterior segment ; a, large dorsal ves- 

 sel ; 6, large ventral vessel ; c, vascular ring, with no branches. 



Fig. 24. — Lateral view of the circulation in one segment; d, branch from the dorsal 

 side of foot: /, branch to the ventral side of foot in the adjacent posterior 

 segment. 

 In the last two figures arrows indicate the direction in which the blood flows. 



Fig. 25. — Dorsal view of two segments showing the vascular network in the lateral 

 appendages and beneath the skin of the back; lettering the same as in fig. 22 ; 

 the large dorsal vessel, a, and the peripheral vessels c, c, show through the trans- 

 lucent walls of the body. 



Fig. 26. — Segment showing the vascular network beneath the skin of the ventral side 

 and in the lateral appendages; lettering as in fig. 22. 



