CEPHALIC FURROWS AND SACS. 85 



10. Cephalic Furrows and Sacs. 



Midway between the tip of the snout and the anterior border of the ganglion in A. lacti- 

 floreus; a furrow runs inwards and slightly forward on the dorsum, ceasing, however, before the 

 central line is reached ; and on the ventral surface a similar though shorter furrow exists, the two 

 meeting in a dimple, furnished with longer cilia, on the side (where the cilia are more active and 

 powerful than usual), which depression leads into the cephalic sac. A short distance behind the 

 ganglia two other superficial furrows occur, each slanting backwards and inwards to meet its 

 fellow of the opposite side in the middle line. These furrows are also continued inferiorly, but 

 with a slightly different direction, so that they meet under the ganglia. The two sets of furrows 

 are very distinctly marked in a flattened head by lateral notches. From the dimple mentioned in 

 connection with each anterior furrow, a thick-walled ciliated duct leads into a considerable 

 ovoid, pyriform, or almond-shaped glandular mass, which lies in front of and rather exterior to 

 the ganglion of the side (Plate XV, fig. 4, m), and from what is seen in translucent species, such 

 as Tetrastemma vermicula, it would appear to end in a cul-de-sac ; the walls, moreover, under 

 pressure are marked by transverse rugse. Towards its first part the duct is surrounded by a 

 minutely granular glandular structure, which usually has a somewhat triangular figure. Several 

 glandular masses lie behind, one to the outer, and another to the inner side in this position. 

 The glandular substance around and behind the posterior part of the ciliated external duct 

 contains numerous granules and finely granular cells. Prom the posterior end of the outer mass 

 in such a view, a structure having the aspect of a pale duct passes obliquely towards the superior 

 lobe of the ganglion, crossing this for some distance in a direction inwards and backwards. 

 Traces of a cavity are apparent at its commencement, and, besides, it is distinguished from the 

 adjoining nerve-trunks under pressure by not being continuous with the ganglion at its 

 edge. In transverse sections of the snout, each sac occupies a position outside the cephalic 

 blood-vessel, and somewhat above it (Plate X, fig. 3, m), and has a special space in the 

 muscular stroma of the head. In large specimens the sacs contain many reddish pigment- 

 grains, and occasionally a large cell filled with coarse granules. Behind the foregoing 

 glandular apparatus lie the coiled ciliated ducts (m), which are sometimes pale and irregularly 

 bulged from included fluid, or else collapsed and minutely granular in aspect. In some speci- 

 mens of A. lactifloreus the commencement of the duct is tinged of a faint reddish hue. There 

 seems to be no ground for the supposition that the sacs are connected with other organs. In 

 T. melanocephala (Plate XIV, fig. 2) they are less dilated than in A. lactifloreus. The coils of 

 the ciliated duct in iV. gracilis are most elaborate, and can be traced a long distance backwards 

 by the side of the nerve-trunk. In N. Neesii the external apertures are not so evident as in 

 A. lactifloreus and Tetrastemma, because the furrows are less distinct when viewed as transparent 

 objects. They are best seen when the ventral surface is upturned, and occur in the angle of the 

 furrow some distance from the margin of the head in this position (Plate XV, fig. 5). The 

 ciliated pit leading inwards is short. Like other parts of A.pulcfier, there is a considerable 

 deviation from the typical form in the shape and position of these sacs, as well as in 

 regard to the furrows. This species (Plate XIV, fig. 11) has also numerous short longitudinal 

 or accessory furrows on the front of the ventral grooves, and thus is allied to A. spectahilis. 

 Instead of lying in front of the ganglia (in the ordinary position under examination), the sacs 



