144 PLAT VHELMINTHES. 
Distomum belongs to the phylum PLATYHEL.- 
MINTHES because of its flattened unsegmented body, 
its simple alimentary canal with no anus, and its meso- 
dermic parenchyma with flame-cell excretory organs. It 
belongs to the class TREMATODA because of its parasitic 
habit with suckers, thick hooked cuticle and complex sexual 
organs. 
II.—TANIA. 
PHYLUM PLATYHELMINTHES. 
- CLASS CESTODA. 
Tenia solium is a common tape-worm inhabiting 
the intestine of the human subject. It is of great length 
Externay (Often _nine to ten feet) and flattened dorso- 
ventrally. The anterior end is extremely small, 
terminating in a knob called the head. The 
body enlarges gradually backwards, and it is broadest at the 
extreme hind-end. It is produced anteriorly into a process 
or rostellum which bears a ring of (22-32) hooks and behind 
them there are four large suckers. A little way behind the 
head there appear transverse constrictions running across 
the body. These get wider apart and deeper towards the 
hind-end, and partially divide the body into a series of 
sections known as proglottides. There may be about 850 
proglottides, of which the broadest are about 3 inch across. 
‘There is no mouth, no alimentary system, and no 
sensory organs, but the. nervous and excretory systems 
are well developed. There is a nerve-ring fn the 
head with two lateral ganglia giving branches to 
the suckers. There pass backwards from them a pair of 
lateral nerves which run throughout the length of the body. 
The excretory system has also a ring in the head and 
four longitudinal ducts. The dorsal and ventral pair do 
not proceed far, but the lateral ducts pass down the entire 
length of the body just inside the nerves. In the posterior 
part of each proglottis they are connected by a 
transverse duct, and in the last proglottis this duct 
opens medially through a contractile vesicle to the exterior. 
Numerous secondary branches break up in the parenchyma 
and terminate in “ flame-cells.” 
Features. 
Nervous. 
Excretory. 
