112 THE HELMINTHES. § 107. 



The fool enters the cavity of the body of Echinorhyncus probably in the 

 same mnnncr, for their skin has great power of absorption.'-^ 



The Acanthoccphali have this peculiarity, that between the skin and the 

 muscular walls of the cavity of the body there is a tliin layer of finely- 

 gramihited 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 nuist be regarded as nutritive or circulatory, aijd 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 a sucker occupying its bottom. From 

 this there passes along the middle line of the neck a thin-walled oesophagus, 

 which is often of an 8-like foi'm. Directly behind the mouth or oral sucker, 

 but sometimes a short distance removed from it, the oesophagus is surrounded 

 by a round 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 rautabile}^^ and jla- 

 vum, the two intestinal tubes, instead of ending coecally, form the arc 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 Jinibriatum, 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 re!rarcling thess organs as mouths, rmim, Distomum, and Po/ijstomicm, the intestinal 



not only in Taenia and Ci/sticercua, but also in bifurcation extends to the posterior extremity of 



Bothriocephalus. I have been unable to find a the body. With Distomum chilostomum, and 



mouth upon the cephalic extremity of the Cestodes, many other sjjecics of this genus living in the Neu- 



as has Melilis (Isis, 1831, p. 131), or upon that of roptera, the whole intestine is reduced to two short 



Taenia solium, as has Owen (Lect. on the Comp. right and left coeca, which are given ofif from the 



Anat. &c. p. 4S, lig. 21, a.). The fossa sometimes end of the oesophagus. 



found upon this last, is due to the retraction of the 3 CrepUn, Nov. Observ. de Entozois, fig. 10, 11. 



circle of hooks, or of the proboscis, within the * This arrangement has been also, but crrone- 



Bheath. ously, assigned to Distomuni tereticolle ; see 



2 Most Ilelminlhologists admit that Echinorhyn- Warner, lichrbuch der vergleichenden Anat. 1834, 



chus receives its food through a small orifice at p. 75, and Creplin, in Erscli and Gruber's Ency- 



the extremity of the proboscis, the sheath of the clop. XXI.X. 1837, p. 314. 



last aiding in suctioil and deglutition. I have been This error is probably due to the inaccurate copy- 

 unable to convince myself of the existence of this ing of figures ; see Ann. d. Sc. Nat. II. 1824, p. 

 orifice, and never have found food in the cavity of 493, PI. X.XIII. fig. 4, 5 ; and Schmalz, Tabulae 

 the sheath. On the other hand, I have often, like Anat. Entozoorum, Tab. A'lII. fig. 2, 3. By refer- 

 Creplin and Mc/i/i.i, seen Echinorhynckus re- ring to the original figure in the Jlcmoir of purine 

 ceive and reject lii]uids through ttie skin. (Mora, de la Soc. do Phys. et d'llist. Nat. de 



1 With Distomum s'lohiporum, the pharynx is Geneve, II. pt. 1, 1823, p. 149, fig. 4, 5), from wluch 

 somewhat removed from tlie oral sucker ; see Bur- these have been copied, there is found no trace of 

 meister, in Wiesm.ann'^s Arch. 1835, II. fig. Taf. a closed, arcuate intestinal canal behind. More- 

 1, 3. In Distomum ecliinatutn, militare and over, Jurine expressly says that he has seen the 

 allied species, the oesophagus is usually very intestinal tubesof Dis/onii/m ferrfZ/coZ/r, ascoeca. 

 long. Kut in Z);'.s/om«m oa;yce/)/ta/it7«, it is very o Baer, in Nov. Act. Acad. &c. XUl. pt. 1, p. 

 Bhort ; and in Distomum ajipendiculatum, il is 536, Taf. XXVIH. ; also D2es?'7i§-, Med. .lahrbuch. 

 entirely wanting, and consequently the intestinal d. k. k. cisterreichischen Staates. XVI. 1834, p. 423, 

 bifurcation is directly behimi the pharynx. fig. 8-11. 



2 In Monostomum, Amphistomum, Holosto- 6 Bucephalus polymorphus is probably a larral 



