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REPORT ON ZOOLOGY, MDCCCXLII : 
1 
require correction in this respect. Leuckart mentions, in all, six species 
of Octobothria, among which three are new, — Octoboth. leptog aster : 
Corporis parte anteriore latiore, lanceolata, posteriore tenuissima, fili- 
formi ; acetabulis anterioribus nullis, posterioribus subpedunculatis, tibu- 
latis. Rapp found it on the branchiae of the Chimcera monstrosa. The 
frame of the clasping-organs here reminds us of Diplozoon paradoxum. 
— Another new species was found by Rapp on the branchiae of the 
Gadus molva, and described by Leuckart as Octoboth. palmatum : — 
Corpore antice et acetabula versus attenuate, medio latiore ; acetabulis 
anterioribus nullis, posterioribus fibulatis, pedunculatis ; pedunculis elon- 
gatis, utrinque palmae formam mentientibus. The double caecum of 
this worm forms, on each side, a beautiful vascular net. The sexual 
opening is placed behind the mouth. The ends of the eight pedicels, 
of the after part of the body, have a groove, which can be opened and 
shut by an anterior and posterior valve-shaped dilatation. The margins 
of these valves are, as in Diplozoon, bordered by amber coloured pieces 
of horn. The eggs are proportionably large, oval, of a brownish-yellow 
colour, and provided with a lid. The length of the worm is 7-8"', 
and its breadth If"". — A third new species is Octoboth. sagittatum: 
Corpore antice attenuate, postice latiore, sagittiformi ; acetabulis duobus 
anterioribus ori proximis, posterioribus fibulatis, sessilibus. This worm 
is a parasite on the branchias of Salmo fario, and has been first men- 
tioned by Schultze and Zahringer, under the name of Cyclocotyle lan- 
ceolatum. Two brown lateral vessels form the intestine, which send ofi' 
ramifications outwardly ; the part of the body provided with clasping- 
organs is constricted ; the four suction grooves, on each side, are very 
close together ; each has two valves, an anterior and posterior, the 
margins of which, as in Octoboth. palmatum, are bordered with several 
pieces of horn. The hook which the Octoboth. lanceolatum possesses at 
the sexual opening, could not be perceived ; a canal passing anteriorly 
contains very large eggs. The length of the animal is 3-4'". Leuckart 
adduces 0. lanceolatum as a fourth Octobothrium, and 0. scombri as 
a fifth ; but, in my opinion, this cannot be specifically distinguished 
from Octoboth. lanceolatum. Octoboth. platygaster, Leuck. (0. Mer- 
langi, Nordm.), has been enumerated as a sixth species ; and as a 
seventh, the 0. hirudinaceum, Bartels, is left doubtful. Of Cyclocotyle 
belones, which Nordmann and Creplin enumerated with the Octobothria, 
Leuckart has mentioned nothing definite. 
From Steenstrup’s ingenious work (Uber den Generationswechsel, p. 
50), it is now evident that the Cercaria, hitherto placed as a separate 
genus, is only a larva-state of different Trematoda, subject to trans- 
mutable generation. In this condition the Trematoda are provided with 
a tail-like apparatus, by the serpentine movements of which the animal 
pushes itself on, quivering in the water. 
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