PROBOSCIS. 55 



possessing much pigmentary and granular, matter. The latter is not well-marked in A. lactifloreus 

 or Tetrastemma, since the entire apparatus is either translucent or white ; but in certain species, 

 as will hereafter be shown, an increase in the granular substance occurs. The longitudinal fibres 

 of the last-mentioned author end at the posterior border of the stylet-region. 



This division is of the same glassy translucency as the reservoir, while both the anterior 

 region and the long posterior are of an opaque- white in the fresh specimen. Externally it 

 has the investing layer (Plate XII, figs. 1 and 2, g) carried from the anterior chamber, and 

 which passes back to the next region. Beneath is a series of very powerful and conspicuous 

 longitudinal muscular fibres (/), apparently to some extent continuous with the most 

 developed longitudinal layer of the preceding region, but few of which pass on to the next. 

 Internally the oblique fibres stretching backwards from the floor of the anterior chamber form the 

 band n (Plate XII, figs. 1 and 2). The rest mingle with the radiating fibres from the central 

 investment. In transverse sections of the anterior part of the region, in the line of the marginal 

 stylet-sacs (Plate XVI, fig. 4), the centre is occupied by the basal granular apparatus, which 

 is generally thrust forward in spirit-preparations, surrounded by its special investments and a 

 belt of circular fibres. The greater part of the region without is occupied by a dense series of 

 radiating fibres, which form the spokes of the wheel, while the ends of numerous longitudinal 

 fibres fill up the spaces between them. If the section is close behind the floor of the anterior 

 chamber, some of the circular fibres which close in the cavity, and other parts of the proper wall 

 of that division are included, while if the cut is a little further back, the granular glands come in 

 the plane of section. The exterior of the region in all cases is occupied by the elastic and longi- 

 tudinal layers. The alternation of radiating or oblique with longitudinal or nearly longitudinal fibres 

 continues to the posterior end of the investments of the basal apparatus, the only change towards 

 the posterior part being the introduction of the ejaculatory duct, and a few circular fibres to its 

 exterior. The pale region behind the basal apparatus has a very complex structure, consisting 

 of densely interwoven fibres that surround the wall of the ejaculatory duct, those towards the cir- 

 cumference showing an arrangement similar to the anterior portion of the region, viz., having the 

 (cut) ends of fibres in the axils of the radiating series. In longitudinal sections of the organ these 

 interlaced fibres are chiefly transverse in direction ; and in some preparations there are numerous 

 granules at the sides, within the somewhat well-defined border formed by the fibres curving 

 backwards (at v, Plate XII, fig. 2), and which corresponds to the lateral arches of the cavity in 

 A. pulcher. The stylet-region proper is distinctly separated at its posterior border from the 

 reservoir by a pale boundary-line under pressure, so that the parts have a somewhat jointed 

 appearance. 



a. The Marginal Stylet- Sacs* 



These organs (v, Plate XII, fig. 2) occupy the exterior (covered only by the elastic coat 

 and the external longitudinal fibres) of the somewhat solid wall of the section immediately 

 succeeding the anterior region, and often cause a distinct swelling under examination. They are 

 conspicuous by their aqueous translucency, as well as by the nail-shaped stylets in their interior, 

 though the exact position of their long axes is rather difficult to determine. In ordinary views, 

 when the animal is examined as a transparent object under pressure, their long diameter is antero- 



