2fi Prof. M'Intosh's Notes from the 



Moreover, that part of the wall of the vesicular tunnel 

 adjoining the gut-wall applies itself to it, whilst the outer 

 part of the cellular structure forms loops in connection with 

 the thoracic glands, which when the sides are flattened 

 present in section the aspect of a tube, as shown by Brunotte 

 (his pi. i. fig. 21). Masses of cells with brown pigment occur 

 on various parts of this cellular membrane, and the trans- 

 parent cells themselves are often grouped near the oblique 

 muscles as they pass to their insertion above and to the 

 exterior border of the great nerve- trunks. A conspicuous 

 feature at this level is the occurrence of a comparatively 

 large aperture through the body-wall just below the bristle- 

 tuft, the finished nature of which shows that it is a permanent 

 structure, but whether in connection with the thoracic 

 glands or otherwise the imperfection of the sections does 

 not enable a decision to be made. The area of the thoracic 

 glands is much larger than in front, the reverse of the con- 

 dition in the Serpulids, and they form complex structures 

 by folding or division. The complexity of these glands is 

 best shown in longitudinal sections, and they fill up the 

 coelomie space in the first two segments. Brunotte de- 

 scribes them as double. Further, toward the posterior part 

 of the glands one tube is found in section to the outer side 

 of the fibres of the oblique muscle and has considerably 

 diminished. Transverse sections of the smaller tubes present 

 an investing membrane lined by nucleated cells probably 

 with internal cilia, all the parts, including the thoracic gland 

 proper, being more delicate and transparent than in Poma- 

 tocerus. Then the gland increases in area and shows various 

 folds or pouches, and the vesicular and cellular strands 

 become abundant, the main gland, to which these are 

 attached, often presenting septa dividing it into two cham- 

 bers. Finally, the gland and its tubular appendages 

 disappear, only the translucent botryoidal tissue being left 

 in strands connected with the mid-ventral region, and passing 

 up to the dorsal longitudinal muscles. Besides the vesicles 

 and cells attached to the membrane a small tube is seen in 

 section, and, moreover, it is clear that this tissue is identical 

 in structure with that attached to the wall of the gut, and 

 nucleated strands pass beneath the canal to be attached to 

 it above the ventral blood-vessel, probably separated from 

 the gut-wall during preparation. Further backward the 

 wall of the alimentary canal is free from this tissue, only a 

 slight development of it taking place posteriorly. 



Segmental Organs. — In the middle of the body a folded 

 tube with transparent nucleated cells lies in the space above 



