112 THE HELMINTHES. «§. 107- 



The food enters the cavity of the body of Echinorkynats 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 fi-om 

 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 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 S-like form. 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.^-' Tlie other forms 

 of the digestive canal are as follows : in Monosto7num midabile,^^^ and ßa^ 

 vicm, 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 Gast erostoinum 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 polymor pints, ^'^^ the structure is similar; and in Fentastomumy 



similar error in regarding these organs as mouths, wiitm, Distomtim, and Polystomum, the intestinal 



not only in Taenia and Cysticercus, but also in bifurcation e.xtends to the posterior e.xtremity o( 



Bothrioc ephalus . I have been unable to find a the body. With Distomum chilostomum, auA 



mouth ujion the csphalic e.\tremity of the Cestodes, many other species of this genus living in the Neu 



as has Mehlis (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 off from thti 



Anat. &c. p. 48, fig. 21, a.). The fossa somethnes end of the oesophagus. 



found ujjon this last, is due to the retraction of the 3 Creplin, Nov. 01)serv. de Entozois, fig. 10, 11, 



circle of hooks, or of the proboscis, within the < This arrangement has been also, but errone 



sheath. ously, assigned to Distomum tereticolle ; set 



2 Most Ilelminthologists admit that Ee/(2norÄi/n- ff^airner, Lehrbucli der vergleichenden Anat. 1834 



chus receives its food through a small orifice at p. 75, and Creplin, in Ersch and Gruher's Ency 



the extremity of the proboscis, the sheath of the clop. XXIX. 1837, p. 314. 



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

 unable to onvince niysi'lf of the existence of this ing of figures ; see Ann. d. So. Nat. II. 1824, p. 

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

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

 Creplin and Mililis, si'cn Echinorhynchus re- ring to the original figure in the Memoir of Jurine 

 ceive and rejcet [ii|uiils thnm.i'li the skin. (.Mem. de la Soc. ,de Phys. et d'llist. Nat. de 



1 With Disluiiviin aloUi purum, the pharynx is Geneve, II. pt. 1, 1823, p. 149, fig. 4, 5), from which 



somewhat ri-niM\-. .1 ii-nm the oral sucker ; see Bur- these have been copied, there is found no trace of 



meister, in Hi, wi/niun's Arch. 1835, II. fig. Taf. a closed, arcuate intestinal canal behind. More- 



1, 3. In Dixliiiiiiiiii I rhinatmn, militare and over, Jurine expressly says that he has seen the 



allied species, th'' m< ipln /u-; is usually very intestinal tubes of yjj.sZomum terre<ifio//ß, as coeca. 



long, liut in Dixiniinnii o ri/rc/ihalum, it is very •'> Haer, in Nov. Act. Acad. &c. XIII. pt. 1, p. 



short; and in Dis/u/iiuiii (i/i/iiiidir.ulatmn, it is 536, Taf. X.XVIII. ; also D/e.sjnfi-, Med. Jahrbuch, 



entirely wanting, and ciiis'iiu.wiily the intestinal d. k. k. österreichischen Staates. XVI. 1834, p. 423, 



bifurcation is directly behiml llii' pharynx. fig. 8-11. 



Ü In Monostomwn, Amphistoinum, Ilolosto- ü Bucephalus pal ymorphus is prohahly alaxvaS 



