60 ANATOMY OF THE ENOPLA. 



cavity into a mere transverse slit. Its inner surface is provided with a series of glands, the larger 

 and more distinct (<r) having minutely granular contents, and easily distinguished from those of 

 the anterior chamber or long posterior region. Towards the opening of the ejaculatory duct the 

 glands are smaller than in the dilated part of the reservoir, and they again decrease in size before 

 the organ narrows to form its posterior channel of communication. In this comparatively large 

 chamber the granules, hereafter to be described, have free scope for the display of their move- 

 ments, and not only do they move themselves, but they cause bodies so large as the compound 

 gland-cells from the posterior chamber, when they happen to be present, to revolve and jerk also, 

 a state of matters that has probably helped to mislead M. de Quatrefages as to the ciliation of 

 the organ. Such, however, is very distinct from ciliary motion. The reservoir diminishes 

 posteriorly, so as to form in the contracted state of the parts a very narrow duct (<£), which 

 by-and-by expands, and becomes continuous with the posterior chamber, the whole forming an 

 hour-glass arrangement, as represented in the various figures. 



The minute structure of the reservoir possesses considerable interest, both as regards beauty 

 and complexity. On reaching the point a (Plate XIII, fig. 10), the elastic and the external 

 longitudinal muscular coats of the proboscis for the most part cease. Before this occurs, how- 

 ever, the muscular fibres (r, Plate XII, fig. 2) peculiar to the region arise, sweep backwards in 

 a beautiful fan-like manner over the reservoir, curve round and meet those from the opposite 

 side, and leave only a small space in the centre posteriorly, through which the channel of commu- 

 nication with the third region passes. When viewed as a transparent object under pressure, or 

 in longitudinal section, the direction of these fibres is backwards and inwards. This great mus- 

 cular mass does not receive accessions from the outer wall, but the whole of the loops come from 

 the front. By the varied crossings of these fibres a felt-like aspect is produced (Plate XIII, fig. 01). 

 In addition, there are circular and longitudinal fibres within the latter, to the presence of which 

 the independent wrinkles of the cavity are due. The longitudinal layer (to) is innermost, and forms 

 a kind of spindle-shaped arrangement ; the anterior fibres — commencing with the ejaculatory 

 duct (of which they form the special wall) — soon expand to cover the dilated cavity of the 

 reservoir, then are narrowed as they surround the channel of communication, and proceeding 

 backwards, merge into the longitudinal coat of the posterior chamber. In some positions 

 these fibres assume an obliquely crossed or spiral aspect in the channel ; but, as in the 

 case of the ganglionic region of the proboscis, this is purely accidental. The margins of the 

 reservoir and the channel of communication are marked under pressure by the ends of muscular 

 fasciculi, especially posteriorly ; an appearance due to the doubling of the looped fibres, but 

 also partly to the presence of the thin circular coat which lies without the longitudinal. The 

 peculiar curvature of the fibres of the reservoir causes a transverse section of its posterior part 

 (Plate XIII, fig. 15) to assume a radiated spiral appearance, the whole reminding one forcibly 

 of Dr. Pettigrew's beautiful diagrams of the arrangement of the muscular fibres of the heart ; 

 and in this case no better structure could have been devised for the complete and forcible 

 evacuation of the chamber. By the contraction of the various fibres, the cavity is squeezed 

 with great force in every direction, like a thick caoutchouc ball or globular syringe in the hand. 

 Its transverse diameter is lessened, and, still more, its an tero-posterior, while a jet of the minutely 

 granular fluid is squirted into the anterior chamber ; and, in spasmodic efforts, even a prolapsus 

 of its glandular lining occurs. In contraction (Plate XII, fig. 9) the entire region is much shortened, 

 and the mass of the looped muscle increased posteriorly. Not only does the peculiar spiral 



