302 Transactions. — Zoology. 



body. Here, too, the skin is wrinkled, forming irregular circular 

 and a few obscure longitudinal ridges. 



Each pajDilla as seen when the skin is examined under the 

 microscope (Plate XVI., fig. 9) is somewhat ovoid in elevation, 

 with a narrowed base of attachment ; it is circular in plan, and 

 about j-^ mm. in diameter. It appears as a thick brown ring 

 with a central light area. Further investigation by means of 

 section shows that the epidermis has macerated away, and that 

 these papillae are entirely dermal, with a wall of connective 

 tissue ; and probably, in Avell-preserved material, this clear centre 

 will not be visible (Plate XVI., fig. 10). In my sections the axial 

 canal communicates with the subdermal spaces, and is traversed 

 by what I take to be a nerve, which breaks up just before reach- 

 ing the apex of the papilla into fine fibrils which are less stained 

 than the nerve itself. Possibly, however, this axial thread is the 

 remains of some secretion from gland-cells which have been 

 destroyed (cf. Shipley's figure of the skin of Onchnesoma, pi. ix., 

 fig. 6, Quart. Journ. Micr. Sci., xxxiii.). But it is unnecessary 

 to discuss this matter here. 



The tentacular crown was invaginated, so that the muscular 

 wall of the introvert had to be slit open in order to ascertain 

 the arrangement. There are numerous simple filiform tentacles 

 springing from an undulating line of origin ; and corresponding 

 with four of these undulations are four well-marked thickenings 

 or ridges along the oesophageal wall, of which two lie on each 

 side, leaving a gap dorsally and ventrally. By pushing forward 

 the wall of the oesophagus so as to cause the tentacles to occupy 

 their proper position when fully extended, I have, as a result 

 of the study of this preparation, been able to make a drawing 

 of what is probably their appearance in life (Plate XV., fig. 2). 



Internally, I was only able to note the following facts : The 

 longitudinal muscles form a continuous sheet. There are two 

 retractor muscles only, attached to the body-wall pretty far 

 forward (my measurement gives 70 mm. below the tentacular 

 crown : this was taken along the muscular wall, which, as above 

 stated, was separated from the skin, hence the discrepancy 

 between this statement and the " length of introvert "). 



The alimentary canal still contains mud, and its wall is pretty 

 firm, but had been thrown into a good deal of disorder by being 

 ejected through the rupture in the body-wall — hence I can give 

 no satisfactory account of its coils. Notwithstanding a certain 

 degree of digestion to which the animal had been submitted, the 

 dorsal blood-vessel still retains an orange-brown tint, and can 

 be traced up to the base of the tentacles and along the dorsal 

 ridge. 



Remarks. — The only species with which \ have been able 



