22 Prof. M'Intosh's Notes from the 



somewhat spiral manner, and an outer series forming a single 

 curve, the larger bristles in this case being above and the 

 smaller at the ventral end. 



Circulation. — In transverse sections from the tip of the 

 branchial fan backward it is found that a clear space, it 

 may be with a translucent coagulum in the centre, appears 

 on the inner curve of each fan dorsally and soon is sur- 

 rounded by a well-defined nucleated wall. Passing back- 

 ward the trunk has a curved lamina attached to it about 

 the level of the fused branchial filaments, and then it 

 occupies a larger internal lamella, with the curved mem- 

 brane distally. Before the chordoid skeleton appears the 

 two trunks are imbedded in the folds, which by-and-by lead 

 to the mouth, being situated on each side of the median 

 fissure (PI. I. fig. 2, bv.), when only slight crenations mark 

 the incipient filaments with their chordoid skeleton, the 

 central chordoid mass having disappeared. These trunks 

 would seem to arise from the division of the dorsal vessel 

 anteriorly, but the sections of the region did not afford 

 absolute proof. Moreover, it has to be noted that, if 

 these are vessels, their contents are devoid of the minute 

 corpuscles present in the trunks elsewhere. Anteriorly the 

 dorsal blood-vessel splits into two great trunks for the 

 branchial fan, and each of these at the level of the chordoid 

 skeleton divides into a series for the filaments, the whole in 

 section having the aspect of a rosette (PI. I. fig. 2, bv.). 

 In the middle of the body the dorsal vessel has disappeared, 

 and a plexus or blood-sinus surrounds the gut, whilst the 

 ventral vessel remains as before ; and this conditions remains 

 to the posterior end. 



In a series of sections of a large example in which the tho- 

 racic glands were unusually spacious, but which (preparation) 

 had been overheated and damaged, deeply stained granular 

 masses occurred inside the membranous sheath around the 

 gullet, such probably representing the blood in the large 

 sinus, though it might be mistaken for masses of sperms. 



At the level of the brain in transverse section the ventral 

 attachment of the collar occurs on each side of the central 

 glandular area, the cuticle and hypoderm of the body-wall 

 bending outward and ensheathing the collar, that part of it, 

 however, covering the central glandular area being much 

 more cellular and granular as well as slightly thicker than 

 the rest. Between the two layers of hypoderm the collar 

 has connective-tissue fibres, cells, and probably muscular 

 fibres, though the latter were not differentiated. The flaps 



