OF THE NEMATOIDS, PARASITIC AND FREE. 587 



I have now to notice considerable modifications of this structure met with amongst 

 other Nematoids. Cloquet* was, I believe, the first to speak of an axial vessel 

 contained within the lateral cords of Ascaris lumbricoides and A. megalocephala. He 

 describes the colour of these lateral bands, in a manner in accordance with my own 

 observations, as very variable in different individuals, adding, " Quelquefois elles sont 

 blanchatres ou grises, d'autre fois d'un rouge assez viff on d'un brun obscur ; mais une 

 chose digne de remarque, c'est que ces couleurs ne sont pas unifonnes dans toute leur 

 longueur; que tres-faibles dans un endroit, elles ont beaucoup d'intensite dans un 

 autre." He also spoke of each vessel leaving its band anteriorly, " s'anastomoser avec 

 celui du cote oppose, en formant une arcade simple dont la convexite est antcrieure, et 

 de laquelle on ne voit sortir aucun filament." Then followed the observations of 

 BianchardJ, who not only recognized but succeeded in injecting these same axial 

 vessels and their anterior communicating branch. He spoke also of an enlargement of 

 the vessel and " une sorte de petite poche" existing on the right side of the arch, 

 which he says " me parait devoir etre consideree comme etant veritablement un vestige 

 de coeur." He maintains also that in each lateral cord there is a second vessel, "tres- 

 grele," lying almost immediately beneath the integument; though he says nothing 

 concerning the anterior distribution of these second vessels or the posterior terminations 

 of either set. He does, however, go so far as to state that this arrangement of the 

 circulatory apparatus is perfectly characteristic of the order Nematoidea, since he has 

 been able to recognize it in the most difibrent types. He says, " J'ai examine les 

 vaisseaux chez les Trichocephales, les Filaires, les Sclerostomes, les Oxyures, etc. ; partout 

 j'ai pu constater une disposition exactement analogue." That this description is incorrect 

 as regards the Ascarides, I have not the slightest doubt, and there is even more reason 

 for believing it at variance with what actually exists in the other genera mentioned. 

 The next anatomist who contributed to our knowledge conceraing these vessels in 

 Ascaris megalocej)hala and A. lumbricoides was Dr. Scii^'eidek §. He ascertained that the 

 arched communication gave off a short straight prolongation in the middle of its course, 

 which brought these vessels into relation with the exterior by means of an apertiue in 

 the mid-ventral region a short distance behind the mouth. The figure he gave on this 

 occasion was rather incorrect, though he has since given a much more truthful repre- 

 sentation of this arch of the vascular system in a recent paper in the same periodical [[ . 

 This representation shows the rudimentary heart of Blanchard to be a large cell filled 

 with granules situated in the thickened parietes of the vessel, at the left side of the 

 arch. Schneider also gives an enlarged representation of one of the lateral bands of 

 Ascaris megalocephala, in which he correctly represents the contained vessel situated 

 near the internal surface of the band, and also pourtrays a chink (Spalt) or split 



• Snr les Vers Intestinaux, 1824, p. 38. 



t This appearance seems duo to the colour of the fluid in the axial vessel. 



t Ann. des Sc. Nat. 3""° ser. t. vii. (1847) p. 126. 



§ Mt'LLEB's Archiv, 1858, p. 426. Taf. sv. 3 a. || Idem. 1863. Taf. i. 



4m2 



