PROBOSCIS. 63 



the fibrillse is so great that they become broadly clavate when ruptured from their attachments 

 (Plate XII, fig. 10,*). 



f. Varieties in the structure of the Proboscis. 



Before reviewing the statements of previous observers with regard to the structure of the 

 foregoing parts, a description of the peculiarities of the regions in other examples of the Enopla 

 may be given. 



In Amphijporus pulcher the anterior region of the proboscis has a pinkish hue, and numerous 

 small clear globules at its commencement. The glandular papillae in the anterior chamber are 

 finer than in A. lactifloreus (which may be taken as the type), and their marginal globules 

 less distinctly marked. In transverse section (Plate XI, fig. 4) the large and somewhat 

 lozenge-shaped columns of the reticulated coat are connected with the outer layer (y), 

 while a process from the opposite angle passes inwards towards the circular fibres (c), so 

 as to cut the great longitudinal layer (d) into a number of separate fascicles, which, in the 

 fine specimen figured, amount to fourteen. When the organ is turned inside out the usually 

 thin external longitudinal coat is thrown into dilated segments separated by the processes 

 from the outer angle of each lozenge-shaped column of the reticulated layer. The mar- 

 ginal stylet-sacs are very large (Plate XII, fig. 6,v), and each contains, in well-developed 

 specimens, from five to nine stylets, a large circular globule, and a granular orange pigment- 

 mass, besides a fluid rich in moving granules, similar to the secretion of the long posterior 

 chamber. It is, however, in the apparatus of the central stylet that the greatest deviation from 

 the typical structure occurs. This (X, Plate XII, fig. 7) is small, -elliptical rather than ovoid, 

 and its granules are very minute. In addition to the ordinary stylet (a) fixed to the anterior 

 end, another (6) projects into its substance, enclosed in a kind of sheath, the point thereof 

 extending forward almost to the butt of the anterior stylet. This reserve-stylet is not in all cases 

 fully formed, but apparently awaits the rejection of its precursor for complete development. 

 Its head lies in a large cavity constituted by a peculiar disposition of the fibres composing 

 the investment of the basal apparatus and the region behind. Instead of the usual wedge- 

 shaped structure, fibres radiate outwards from the sides of the organ, curve backwards, and 

 arch over a large cavity (Plate XII, fig. 6, ov) filled with a clear fluid, part of the floor 

 being formed by the anterior fibres of the reservoir. In certain states of contraction the 

 reserve-stylet is thrust backwards, so that its butt rests on the latter chamber, a position 

 quite easily attained, on account of the yielding nature of the cavity and tissues placed imme- 

 diately behind and around it. Streaks, due to the granular glands, are also observed passing 

 from the central apparatus along the arch of the fibres. The glands themselves are distinct 

 enough if the specimen is not too much pressed. The great development of the cavity behind 

 the central apparatus might be supposed to assist in the rapid formation of the reserve-stylet, yet it 

 cannot be absolutely necessary for its development, since the stylet is as readily replaced in front of 

 the granular structure in other species. The ejaculatory duct is large, and being surrounded by a 

 very yielding region, is more mobile than in the typical form. The clear globules interspersed 

 amongst the looped fibres of the reservoir are numerous, so that under examination the cavity seems 



