PEOSTHEOOSACTEE. 93 



membranous -^ngs analogous to those observable in many true 

 Ascarides. In this situation also the calibre of the body itself is 

 considerably increased (Fig. 2, Plate VI.) In the genus Prosthe- 

 cosacter generally, these wings are prolonged beyond the caudal 

 extremity in the form of lobed appendages or tentacula, but they 

 vary in shape in the different species of the genus. In P. convo- 

 lutus they are perfectly oval, transparent, and free from either 

 longitudinal or transverse striae. In their interior are two fleshy 

 or muscular papiUas, protected by a fibrous envelope or extension 

 of the true dermis. These organs are probably designed to assist 

 in the copulatory act. Between the tentacular lobes and the alae 

 proper, there are also two intermediate membranous folds, whose 

 surfaces, though devoid of transverse stri«, display a series of 

 parallel vertical phc«, which are not always equally conspicuous ; 

 and at the extremity of the tail, in the central Hne, there is also a 

 thin sucker-like disk, apparently due to the free protruding end of 

 the sheath of the penis. This latter organ is double or bifurcate, 

 the separate divisions being very long, filamentary, and uniform in 

 thickness throughout ; whilst within the body they are readily 

 distinguished by their bright, brownish, yellow colour (Fig. 2, 

 Plate VI.) In P. infiexus the horns of this organ are compara- 

 tively short, thick, and unciform. 



The digestive system, speaking generally, consists of a simple 

 tube passing in a straight direction from mouth to anus ; but the 

 oesophageal portion is very well defined, and is succeeded by a 

 short stomachal bulb, which opens into the club-shaped, capacious 

 upper end of the long intestine (Fig. 1, Plate VI.) In the male 

 the rectum appears to terminate in a general cloacal cavity, having 

 its final outlet between the caudal lobes ; but in the female the 

 lower end of the intestinal tube opens separately by a distinct anal 

 orifice situated immediately behind the vulva, and almost at the 

 extremity of the peculiar obliquely truncated tail (Fig. 3, Plate VII.) 



The internal reproductive organs as developed in the male con- 

 sist of a simple tubular secreting gland forming the testis, which is 



