226 
ALFRED GIARD. 
distinctly segmented, and tapers slightly towards the pos- 
terior end ; while the surface is marked by very fine longitu- 
dinal striae, as in Opalina, though in a much more minute 
degree. Anteriorly is a conical portion (a), composed of 
three rather indistinctly marked segments. Two evident 
annuli (6) succeed, the posterior part of the last being nar- 
rowed, so as to cause a constriction of the body-'wall. Be- 
hind are six nearly equal divisions (c), each often appearing 
double, that is, has a broad anterior and a narrow posterior 
annulus. The posterior region (d) consists of three indis- 
tinct segments. The body is minutely granular throughout, 
and an internal cavity is apparent from the fourth segment 
to the last, commencing in the former by a rounded end, and 
terminating just within the border of the latter. No aper- 
ture is observed at either end. The opaque, ovoid, granular 
bodies (plate xviii, fig. 18), scattered profusely throughout 
the infected portions of the Lineus, are evidently early 
stages in the development of this species, and they, too, are 
ciliated. On subjecting them to gentle pressure (fig. 19), 
transverse segmentation is apparent, the number of segments 
varying according to the degree of advancement. The para- 
sites are very delicate structures, and in the free state soon 
break up into cells and granules, after discarding their cilia, 
as above mentioned. Transverse section of the affected 
worms shows that they occur both in the skin and in the 
walls of the digestive tract, their ravages in the pigmentary 
layer of the former tissue causing the curious appearances 
which led to their detection. It is a somewhat difficult 
point to determine whether the skin, muscles of the body- 
wall, or digestive canal, constitute the common area of this 
creature’s depredations, whether it is piercing the former on 
its way to the surface, or passing to the alimentary cavity to 
be voided per anum. The characteristically segmented con- 
dition of the mature specimens and their internal structure 
exhibit a higher type of organisation than the ordinary 
Opalina. Professor Keferstein found a very similar parasite 
in the stomach of Leptoplana tremellarisy but he did not 
describe it further than simply mention, under the explana- 
tion of the plate, that it is an enigmatical structure. The 
centre of the body is occupied by a double row of large cells 
in his figure.” 
Such are the details, certainly rather incomplete, it must 
be conceded, which w’e have been able to find in earlier 
writers touching the curious animals which we have 
designated by the name of ORTHO^’ECTIDA.^ 
1 We published in the ^ Comptus Kendus de I’Academie des Sciences ’ 
