92 CEYLON PEARL OYSTEE REPORT. 



The two suckers are equal in diameter, that of each equal to one-third of the width ot 

 the body at its widest part. The posterior or ventral sucker (v.s.) is placed just behind 

 the middle point in the longitudinal axis, its anterior margin approximately coinciding 

 with this point. The muscular structure of the suckers presents no unusual feature. 



Transverse rows of minute spines, closely and regularly disposed, beset the cuticle. 

 The points are directed backwards, and as a rule they alternate in position with 

 those of the row in front. The rows encircle the body, and, being arranged with 

 perfect regularity, they impart a distinct appearance of annulation. There are about 

 150 or more of these encircling rows (Plate III., fig. 57, c.s.). 



Two black eye-spots are conspicuous, even when the larva is viewed within its 

 capsule (Plate III., figs. 54 and 55, e). One lies on either side, close to the junction 

 of the oral sucker with the muscular pharynx. The diameter of each eye is equal 

 to the width of two of the transverse rows of cuticular spines. 



A wide aperture in the centre of the oral sucker opens into its capacious 

 funnel-shaped cavity, a chamber continually varying in size. The mouth lies at the 

 base of this funnel, whence a short buccal passage leads directly into the muscular 

 pharynx (ph.), elliptical in optical section. There is practically no oesophagus, and 

 the two long tubular digestive creca (d.c.) arise close to the pharynx. Each of these, 

 as it passes backwards, curves outwards till it approaches close to the lateral margin, 

 thereafter pursuing a nearly straight posterior course. The crcca terminate at a 

 point close to the anterior bolder of the excretory vesicle (c.r.). They are never 

 distended with food material, as happens in the case ol the succeeding species; little 

 is to be seen save a number of rather large clear globules. All the organs are, 

 indeed, remarkably clear and free from the massing of opaque granules so frequent 

 in many Cercariaj and which is so marked a feature of the species next to be 

 described. 



The excretory system consists of two tubular lateral trunks extending the whole 

 length of the body. Anteriorly, in the pharyngeal region, they are much convo- 

 luted ; posteriorly they empty into a capacious median vesicle which communicates 

 with the exterior by means of a narrow funnel-shaped pore at the hinder end. The 

 excretory vesicle varies considerably in form ; sometimes, as when the larva is lying 

 within its capsule, it is broadly ovate, the narrow end directed posteriorly (Plate III., 

 fig. 54, c.r.) ; at other times, when the worm is crawling about after liberation, the 

 A^esicle shortens and widens, and appears as a broad transverse chamber, roughly 

 triangular in outline, the base directed forwards (Plate III., fig. 55, c.v.). The 

 epithelial cells lining its interior are very conspicuous ; they consist of very large 

 cells, markedly convex on the free surface. 



Two paired glands, which appear to be the male gonads, are present. They are 

 situated laterally, one on either flank of the ventral sucker. Each is an elongated 

 sac, broader behind than in front, and full of denselv packed cells containing 

 numerous clear globuledike bodies. No ovary can be traced. 



