114 



THE HELMINTHES. 



§109. 



tions, and which terminates in a short muscular rectum. Tlie proper intes- 

 tine is of a brown, greenish, or dirty yellow color, which is due to its walls 

 being formed of compact cells filled with colored granules. The loose and 

 cellular walls, having very feeble peristaltic movements, are surrounded 

 externally by a kind of dense peritoneum, and lined internally by a very 

 fine epithelium.*''' In some species of Ascaris, the intestine is lengthened 

 into a caecum at its junction with the oesophagus."^' 



§109. 



There are observed, here and there, only traces of appendant organs of 

 the digestive canal. 



In many Trematodes, there are upon each side of the neck, two more or 

 less developed cords or canals, of a cellular aspect, and of a pale yellow 

 color by direct light. They pass towards the mouth, open perhaps into its 

 cavity, and have a function, probably, like that of salioury organs.'-^^ In 

 many Nematodes, two or four caeca extend from the cephalic extremity 

 along the (Esophagus, and as they open distinctly into the oral cavity, it is, 

 therefore, the more probable that they should be regarded as salivary 

 organs.*-* The same signification should be given to the coecal appendage 

 found in many species of Ascaris, which extends from the constriction of 

 the oesophagus to the beginning of the intestine.*'^' 



Hepatic organs have been found nowhere but in the Nematodes; but it 

 may be that the granular cells in the thick walls of the intestinal canal, 

 take their place. 



5 This epithelium has samjtimes special inequali- 

 ties, which, with Ascaris osculata, and spioutige- 

 ra, fjnn a regular zig-zag scries, resembling the 

 valves of the intestinal mucous membrane of same 

 vertebrates. With Ascaris aucta, they have the 

 form of long, sharp villosities. 



6 This caecal appendage, accompanied usually 

 with a constriction of tlie posterior end of the 

 oesophagus, was first observed by Mehlis (Isis. 

 1831, p. 91, Taf. II. fig. 16, 17, IS). It is found 

 with many Ascaris, but its length is very variable. 

 In Ascaris heterura, semiteres, and ensicaudata, 

 it is very short, and protrudes scarcely beyond the 

 oesophageal canstriction ; while in Ascaris depres- 

 sa, auata, an<;ulata, and mucronata, it reaches to 

 tlie middle of the (esophagus, and in Ascaris spi- 

 culigera, osculata, and the species described as 

 Filaria piscium, it extends nearly to the cephalic 

 extremity.* 



1 Thesi! glandular-like organs are often very 

 distinct iii'the cercarian larvae of the Trematodes, 

 and in many adults of Mnnostomum, and Disto- 

 mum ; see IViegm.in.n''s Arch. 181}, II. p. 322. 



2 Mehlis (Isia, 1831, p. 8 J, Taf. II. fig. 6) has 

 observed with Strongylus arrnatus, an annular 

 vessel surrounding the mouth, wliich commuui- 



cates with it directly, and also with two cards 

 accompanying the cesophagus. According t) him, 

 there is also a similar disposition with Strongylus 

 hypostomus, and tetracanthus. 



Similar appendages, analogous to salivary or- 

 gans, occur, according to Owen, in the new genus 

 Gnathosoma, as four caeca surrounding the oeso- 

 phagus, and opening into the mouth {IFieg- 

 mann's Arch. 183S, I. p. 134). With Cheiranan- 

 thus, and Ancyr acanthus, there are four similar 

 organs, and Diesing is certainly in error in 

 regarding them as analogous to the ambulacral 

 vesicles of the Echinod.-rms (.4nn. d. Wiener Mus. 

 II. Abth. 2, p. 221, 226, 228, Taf. XVIl. fig. 8, 9, 

 Taf. XVIII. fig. 3). I am disposed to regard as 

 salivary organs, also, the two long caeca which 

 pass from the mouth along the oesophagus of 

 Strongylus s trial us. 



S I have discovered a similar oesophageal ap- 

 pendage in a group of Ascaris known as Filaria 

 piscium (^fViegmanii's Arch. 1838, I. p. 303) ; 

 such are, Ascaris mucronata, angulata, oscu- 

 lata, spiculigera, aucta, acus, and labiata. It is 

 remarkable that with the e.vception o the last two, 

 all these have also a caecum upon the intestine. 



* [ § 103, note 6.) See, for the alimentary canal 

 of Ascaris infecta, Leidy (A Flora and Fauna 

 within living animals, Smithsonian Conlrib. V. Art. 

 2, p. 43, PI. VI. fig. 1-7). He divides it into a 

 strongly muscular gizzard, a cylindroid intestine 

 lined with he.xahedral epithelium, and a pyriform 

 rectum. 



See also his description of that of Streptoso- 

 mum, Thelastomum, &c. (Ibid. p. 49). In The- 



lastomum appendiculatum, there is this pecu- 

 liarity, that the intestine commences by a broad, 

 deeply sinuate, cordiform dilatation, which rapidly 

 narrows to a short, cylindroid portion, and then 

 sends off a long, capacious, gourd-form receptacle, 

 or diverticulum, and afterwards proceeds back- 

 wards to the rectum, and in its course, in the vi- 

 cinity of the generative aperture, performs a singl» 

 short convolution. — Kd. 



