254 ZOOLOGY sect. 



ventral, either median or lateral, sometimes at the posterior end. 

 There are two testes, sometimes fused into one, sometimes broken 

 up into more or less nnmerons follicles, but always provided with 

 only two vasa deferentia. There is a single germarium, not un- 

 commonly lobed or divided up into a number of separate parts. 

 A receptaculum seminis, or a Laurer's canal, or both, are present. 

 The vitelline glands are, in most instances, paired, more or less 

 richly branched, extending towards the lateral borders of the 

 body. 



The genus Fasciola is a member of the sub-family Fasciolince of 

 the Distomidce, and this is distinguished from the other sub-families 

 by the following characteristics. The Fasciolince are broad, leaf- 

 like Distomidce, with the integument spinose or scaly. They have 

 a well-developed pharynx. The intestinal limbs are simple or 

 branched. The genital aperture is median, and situated in front 

 of the posterior sucker. The testes are situated one behind the 

 other, directly or obliquely: they are either simple, divided into 

 lobes, or branched. The ovary is immediately in front of the 

 testes, the uterus in front of the ovary. A Laurer's canal is 

 present. The receptaculum seminis is absent or small. Among 

 the many genera into which this sub-family is now divided the 

 genus Fasciolcc presents the following distinctive features : — The 

 anterior end is distinctly differentiated into a head-lobe; the 

 intestinal limbs have long branched diverticula on the outer side, 

 short on the inner ; the gonads are all richly branched ; there is 

 no receptaculum seminis. 



Tcenia solium is one of the many species of the genus Tcenia, 

 of the family Toeniadce, which is distinguished from the other 

 families of Cestodes by the possession of four suckers, with or 

 without a circlet of hooks, and by the development of well-defined 

 proglottides which become separated off when mature. 



3. General Organisation. 



General External Features. — As the name of the phylum 

 denotes, the body in the Platyhelminthes is, in the great majority 

 of cases, much compressed in the dorso-ventral direction ; very 

 thin, so that when very short it may be described as leat- 

 like, or, when more elongated, as ribbon-like ; or thickish in 

 the middle and becoming thinner towards the margin. Some, 

 however, have the body comparatively thick, usually with a certain 

 amount of dorso-ventral compression; a few are approximately 

 cylindrical or fusiform. The symmetry is always bilateral (p. 43), 

 the radial arrangement of parts so prevalent in the Ccelenterata 

 and primarily, as we have seen, associated with a fixed or stalked 

 condition, never being observable. A Flat- Worm has dorsal and 



