THE HELMINTHES. $ 107. 
112 
The food enters the cavity of the body of Echinorhyncus probably in the- 
same manner, for their skin has great power of absorption. 
The Acanthocephali have this peculiarity, that between the skin and the: 
muscular walls of the cavity of the body there is a thin layer of finely-. 
granulated parenchyma, often of an orange or yellow color, which is traversed 
by longitudinal and transverse canals. ; 
These canals, having no proper walls, form a continued vascular system,. 
and contain a liquid filled with granules and vesicles. As this system is. 
completely closed, and cannot therefore receive nutritive substances from 
without, it must be regarded as nutritive or circulatory, and not digestive,. 
as it has been by many naturalists. 
§ 107. 
In the other groups of the Helminthes the digestive organs are pretty: 
generally well developed. : 
The Trematodes have a mouth situated usually upon the border of the. 
cephalic extremity, and where there is asucker occupying its bottom. From 
this there passes along the middle line of the neck a thin-walled cesophagus,. 
which is often of an S-like form. Directly behind the mouth or oral sucker, 
but sometimes a short distance removed from it, the oesophagus is surrounded 
by around or oval muscular pharynx.” From the extremity of this pass 
off, usually, two blind intestinal tubes, which, passing along both sides of 
the body, extend generally to its posterior extremity.” The other forms 
of the digestive canal are as follows: in Monostomum mutabile,” and fla- 
vum, the two intestinal tubes, instead of ending coecally, form the are of a 
circle; in Aspidogaster, a simple and uniform intestine succeeds upon the 
pharynx, and ends in a coecum at the posterior extremity of the body ;® 
in Gasterostomum fimbriatum, this canal is very short, and terminates in. 
the same way, but there is a mouth in the middle of the ventral surface; 
in Bucephalus polymorphus,® the structure is similar; and in Pentastomum, 
similar error in regarding these organs as mouths, 
not only in Taenia and Cysticercus, but also in 
Bothriocephalus. I have been unable to find a 
mouth upon the cephalic extremity of the Cestodes, 
as has Mehlis (Isis, 1831, p. 131), or upon that of 
Taenia solium, as has Owen (Lect. on the Comp, 
Anat. &c. p. 48, fig. 21, a.). The fossa sometimes 
found upon this last, is due to the retraction of the 
circle of hooks, or of the proboscis, within the 
sheath, : . 
2 Most Helminthologists admit that Echinorhyn- 
chus receives its food through a small orifice at 
the extremity of the proboscis, the sheath of the 
last aiding in suction and deglutition. I have been 
unable to convince myself of the existence of this 
orifice, and never have found food in the cavity of 
the sheath. On the other hand, I have often, like 
Creplin and Mehlis, seen Echinorhynchus re- 
ceive and reject liquids through the skin, 
1 With Distomum globiporum, the pharynx is 
somewhat removed from the oral sucker ; see Bur- 
meister, in Wiegmann’s Arch. 1835, IL. fig. Taf. 
1, 3. In Distomum echinatum, militare and 
allied species, the cesophagus is usually very 
long. ‘But in Distomum oxycephalum, it is very 
short; and in Distomum appendiculatum, it is 
entirely wanting, and consequently the intestinal 
bifurcation is directly behind the pharynx. 
2In Mon Amphist Hy, 
lost 
mum, Distomum, and Polystomum, the intestinal 
bifurcation extends to the posterior* extremity of 
the body. With Distomum chilostomum, and 
many other species of this genus living in the Neu 
roptera, the whole intestine is reduced to two short 
right and left coeca, which are given off from the 
end of the cesophagus. $ 
3 Creplin, Nov. Observ. de Entozois, fig. 10, 11. 
4This arrangement has been also, but errone 
ously, assigned to Distomum tereticolle ; see 
Wagner, Lehrbuch der vergleichenden Anat. 1834,. 
p. 75, and Creplin, in Ersch and Gruber’s Ency 
clop. XXIX. 1837, p. 314. 
This error is probably due to the inaccurate copy- 
ing of figures; see Ann. d. Sc. Nat. If. 1824, p. 
493, Pl. XXIII. fig. 4, 5; and Schmalz, Tabulae 
Anat. Entozoorum, Tab. VIII. fig. 2,3. By refer- 
ring to the original figure inthe Memoir of Jurine 
ate de la Soc. de Phys. et d’Hist. Nat. de 
enéve, IT. pt. 1, 1823, p. 149, fig. 4, 5), from which 
these have been copied, there is found no trace of 
a closed, arcuate intestinal canal behind. More- 
over, Jurine expressly says that he has seen the- 
i 1 tubes of Dist terreticolle, as coeca. 
5 Baer, in Nov. Act. Acad. &c. XIII. pt. 1, p.- 
536, Taf. XXVIII. ; also Diesing, Med. Jahrbuch. 
d.k. k. ésterreichischen Staates. XVI. 1834, p. 423,. 
fg. 8-11. 
? ? 
Bucephalus polymorphus is probably a larval 
