112 H. CHARLTON BASTIAN ON THE STRUCTURE AND 
Much doubt and uncertainty prevails amongst anatomists concerning the nervous 
system of the Nematoid worms; so that little or nothing definite can be said with regard 
to its arrangement in the order generally. 
Walter's* elaborate and precise observations on the anatomy of Oxyuris ornata seem 
to show that this animal possesses a most complex and highly organized nervous 
system, consisting of cerebral and caudal ganglia, from which, and from the cords con- 
necting them, numerous branches are supplied to all parts of the body. But it would be 
desirable that such observations should be confirmed by other anatomists, since in 
another species of the same genus, a common human parasite, Oxyuris vermicularis, 
no neryous system has as yet been discovered. ! 
Blanchardt, following Cloqueti, in his description of Ascaris lumbricoides considers 
it to possess a dorsal and a ventral, median, longitudinal, nervous trunk, and, more- 
over, considers this to be the typical arrangement of the nervous system in the 
Nematoidea. This opinion is shared by many other anatomists; but, when speaking of 
the circulatory system of the Guineaworm, I shall presently point out why it appears to 
be untenable. 
What I have just described as existing in Filaria medinensis agrees with the distri- 
bution of the principal nervous trunks in the Nemertidæ and some of the Trematode 
worms; and a careful examination of recent specimens of the Guineaworm may 
perhaps hereafter show some central connecting ganglia anteriorly, and thus render the 
resemblance more complete. | 
Organs of Circulation.—The representatives of this system met with in the Guinea- 
worm belong, doubtless, as in its allies the Teeniadze and the Trematoda, rather to the 
“ water-vascular system” and the function of respiration than to the propulsion of true 
blood; yet still, in the presentimperfect state of our knowledge, I have thought it better 
to describe them under the above head. 
Four equidistant longitudinal vessels extend through the whole length of the body, 
situated, like the nervous cords, in the midst of a pulpy substance beneath the peri- 
toneal membrane. The two which occupy the median line of the dorsal and ventral 
regions respectively are much larger than the two lateral vessels. All four extend from 
one extremity of the body to the other; but how they terminate in either direction I 
have been unable to determine, neither have I succeeded in finding any external aper- 
ture with which they communicate, such as is generally met with in connexion with the 
water-vascular system of the Annuloidea. 
The dorsal and ventral vessels are in all respects similar, occupying the median inter- 
muscular interval in each situation (Pl. XXI. fig. 22, e, f). They have an opake-white 
colour when seen with a powerful lens ; but when examined under the microscope by trans- 
mitted light, they are found to be very delicate thin-walled tubes (Pl. XXI. fig. 28). They 
pursue a very undulating course, and are by no means of one uniform calibre, being 
frequently bulged at intervals. "Throughout the greater part of their extent they are 
* Zeitsch. für wissen. Zoologie, vol. viii. 1857, p.163. 
T Ann. des Sciences Naturelles, 3m série, tom. xi. 1849, p. 138. 
I Anatomie des Vers intestinaux, Paris, 1824, p. 38. 
