G22 DE. H. CHABLTON BA8TIAN ON THE ANATOMY AND PHYSIOLOGY 



It seems to me that in the present state of our knowledge we may be justified in looking? 

 upon the Nematoidea, and in all probability the Gordiacece, as close allies of the Echino- 

 dermata, leading to and connecting these with the Scolecida through their affinities 

 to the Acanthocephala. 



In the first place, the nervous system of the Nematoids is remarkably similar to that 

 of the Echinoderms. In all adult specimens it is described by Professor Huxley as 

 " a ring-like or polygonal ganglionated cord situated superficially to that part of the 

 ambulacral system which surrounds the mouth, and sending prolongations parallel with 

 and superficial to the radiating ambulacral trunks"*. And elsewheref he states that 

 " the circle round the mouth has rather the nature of a commissure than of a ganglionic 

 centre." Scarcely anything can be more close than the correspondence of this description 

 with the actual condition of things fully proved to exist in certain genera of Nematoids. 

 This similarity is especially notable as regards the characters of the oesophageal ling : 

 the agreement is here complete, and any difference as regards the arrangement of peri- 

 pheral branches is nothing more than might be expected from the diversity in external 

 form of the respective animals. If we take next the vascular system — accepting the 

 views propounded by Professor Huxley as to the probable homological identity of the 

 water-vascular system of the Scolecida with the ambulacral system of the EcMnodennata 

 — there can be little doubt that the so-called ventral glands in some, and the much more 

 developed system of canals in other Nematoids, each having a similar communication 

 with the exterior, can have their homologues only in these two systems, although their 

 relationship is much more marked to the vessels of the Scolecids than to those of the 

 Echinoderms. In both Nematoids and Scolecids the tubes immediately communicating 

 with the exterior have been observed contracting and dilating in a kind of rhythmical 

 manner, and the contents of each have been seen to consist of a clear fluid containing a 

 larger or smaller quantity of suspended molecules. And the fact that as yet no cilia 

 have been recognized in any part of this system of canals in the Nematoids — even 

 though they are really absent, and their non-discovery has not been due merely to the 

 intrinsic difficulties of the investigation — seems to be no real objection, since though 

 such ciliated prolongations in connexion w ith the non-ciliated contractile tubes have been 

 distinctly recognized in many Trematoda and Tceniada, still there are some of the fonner, 

 such as Distoma excisum observed by Huxley, and Bistoma tereticolle, D.perlaUim, and 

 D. nodulosum, together with Amphistoma subclavatum, according to Aubeet, in which "no 

 cilia at all exist in any part of the water-vascular system, so that in these Trematoda its 

 condition is, as it w^ere, diametrically opposed to that which it exliibits in Aspidogastef'X, 

 The method of development of these tubes in the Nematoids according to all ajfriori 

 possibility, and also from what I have seen in the young of Bracunctilm medinensis, 

 appears to be similar to that by which the water-vessels of the Scolecids and the ambu- 

 lacral vessels of the Echinoderms originate ; and for the reasons before stated^, I think 



* Elements, p. 46. t Med. Times, 1856, iL p. 635. 



t Med. Times, 1856, ii. p. 133. § See p. 597. 



