OF TIIE XEMATOIDS, PAEASITIC AND FREE. 567 



pheral filaments in Oxynris omata, though he has since very honestly confessed the 

 errors into which he had fallen on that occasion, and now admits to a great extent that 

 no such system is to be met with in the animal in question. 



In the paper " On the Structure and Nature of the Dracunculus" *, I myself described 

 as belonging to the ner\'ous system two very peculiar ganglionated cords which traverse 

 the centre of each intermuscular lateral space. I have since repeatedly examined these 

 structures, and although I now entertain considerable doubts about their belonging to 

 the nervous system, I have no modifications to make in the description I then gave of 

 their actual structure. They remain a perfect puzzle to me, and I can offer no sugges- 

 tions as to their real nature. 



In his recent work on ' Entozoa,' Dr. Cobbold expresses his belief that what is now 

 looked upon by most anatomists as an axial vessel or excretory canal in the lateral bands, 

 should rather be relegated to the nervous system. Speaking of these structures in 

 Ascaris lumhricoides, he says, " I find the lateral lines characterized by a band of large 

 granular cells, in the centre of which lies a well-marked double-bordered canal con- 

 taining fine granular matter. I cannot call the inner tube a true nervous cord, but at 

 the same time I am willing to believe that it represents a rudimentaiy condition of a 

 true nerve-system." This view is entirely unsupported by evidence, and is, moreover, 

 directly opposed to the existing state of knowledge. 



At last, after this maze of conflicting statements, we come to something more definite, 

 and likely to bear the test of scrutiny, in the recent accurate investigations of ScHXEiDERf 

 upon the nervous system of the Nematoids ; the clue to which was given by the observation 

 of LiEBERKUHN', Wedl, and himself at an earlier period, of a pale band surrounding the 

 anterior part of the oesophagus. Bearing this in mind, and following it up at a later 

 period by dissections conducted in the most careful manner, he succeeded in detecting 

 in Ascaris megalocepJmla and other Nematoids what is undoubtedly the most essential 

 portion of their nervous system. 



In Eberth'sJ most interesting memoir, published about the same time, upon the 

 anatomy of both free and parasitic Nematoids, after mentioning diverse structures which 

 might possibly be taken to represent parts of a nervous system, he evidently remains of 

 the opinion that, so far as he has seen, there is no structure in the Nematoids that he 

 could with confidence look upon as the representative of such a system. He appears, 

 however, never to have carefully examined either A. lumbricoides or A. megalocephala, 

 which are the most favourable species at present known for the detection of this structure. 

 Up to within quite a recent period the views that I had arrived at (quite independently) 

 accorded almost precisely with those held by Eberth. I was far from disposed abso- 

 lutely to deny the existence of a nervous system in the Nematoids, but after a pretty 

 careful examination of many species I had utterly failed to recognize anything which I 

 could look upon as belonging to a nervous system, and must confess felt very sceptical 



* Trans, of Linn. Soc. vol. xxiv. p. 111. f Eeich. and Du Bois-Retm. Archiv, 1863, 8. 1. 



J Untersuch. iiber Nemat. 1863. 



