14 Prof. M'Intosli's Notes from the 



substance. The curve of the larger flap, which appears to 

 be normal, would seem to show that the connective tissue in 

 its middle is more or less elastic. Viewed in section the 

 central rib presents cuticular and hypodermic coverings, 

 then the transparent skeletogenous layer, which shows no 

 evidence of cameration, and in the centre the tinted coagu- 

 lable substance surrounded by the granules. In all proba- 

 bility this is a blood-vessel, and a trunk is seen in other 

 forms, such as Spirographis, running up the centre of the 

 skeletogenous sheath which ends in a delicate tip; and in 

 the basal region of the tentacle numerous fine twigs ramify 

 in the tissues. In sections from the tip downward the 

 longer curved flap lies within the outer branchial row, 

 between it and the tip of the inner row, and it has a blood- 

 vessel at its edge. 



Nervous System. — The cephalic ganglia in section (Pi. I. 

 fig. 1, eg.) form two ovoid masses, connected by a broad 

 commissure, and situated about the commencement of the 

 chordoid skeleton of the region. The outer and more 

 cellular part of each ganglion stains slightly, whilst the 

 inner region and the commissure are pale. Moreover, at 

 the outer edge of each mass is a pale area in section sur- 

 rounded by brown pigment apparently representing an eye 

 (PL III. fig. 14, oc), and thus akin to the deep-seated eye of 

 the ammocete stage of the lamprey, though it does not reach 

 the surface in adult life. The capsule is consistent and 

 stains, the centre being pale as if functioning as a lens, 

 whilst the brown pigment seems to be chiefly massed on the 

 inner border. Between the dorsal mass of muscle and the 

 ganglia is a large vascular trunk on each side — the branchial — 

 besides a closely reticulated tissue, the same tissue occurring 

 laterally where the lower ends of the muscles cease; whilst 

 the cesophagusis in the middle line below the commissure, and 

 its sheath of muscle and connective tissue abuts inferiorly on 

 a broad glandular hypodermic area ventrally, the apex of 

 which is joined to the oesophageal sheath by the same 

 reticulated connective tissue mentioned previously. In front 

 of the ganglia a large ccelomic space and a vascular trunk 

 lie at the base of the branchial apparatus before separation 

 into branches for the filaments. 



The sections, at the separation of the great nerve-cords 

 from the cephalic ganglia were somewhat imperfect, but 

 these trunks appeared to follow a similar course to those of 

 Spirographis, as described and figured by Meyer * and 

 others. 



* Mitt. Zool. Stat. Neapel, Bd. vii. Taf. xxiii. fig., andBd. viii. pp. 537- 

 509. 



