Tse MuicroscopicaL News 
AND 
NORTHERN MICROSCOPIST. 
INO: 30. JUNE. 1883. 
ON) (GY BO DAC T VU 'S Ea G Ae Nese 
By HERBERT C. CHapDwIck, F.R.M.S. 
YRODACTYLUS ELEGANS is a trematode worm of parasitic 
habit. It was discovered in Germany by Nordmann, and 
afterwards described more or less fully by Creplin, Dujardin, Von 
Siebold, Diesing, Wagener, and Von Beneden. 
The discovery of its existence in England was announced to the 
Linnean Society in the year 1860, by C. L. Bradley,, Esq., F.L.S., 
who found it on the sticklebacks inhabiting the ponds on Hamp- 
stead Heath. In 1861, a translation of Wagener’s paper appeared 
in the “ Quarterly Journal of Microscopical Science,” and in the 
following year, 1862, a short paper by Dr. Spencer Cobbold ap- 
peared in the same journal, in which he stated that he had found 
the Gyrodactylus on the fins of the sticklebacks inhabiting the 
Serpentine, associated with large numbers of ‘Trichodinz. I have 
recently found it on sticklebacks from a pond at Eccles, again 
associated with large numbers of Trichodinz. In form, Gyro- 
dactylus closely resembles the common sea-mouse, Fig. 43, being 
tongue-shaped, the dorsal surface being convex, and the ventral 
surface being flattened. The average length of the specimens 
observed by Wagener was ;% th of an inch, but the specimens which 
I have had under observation were larger, their average length 
being ;4;th of an inch. The anterior extremity of the animal is 
divided by a median fissure or cleft into two cephalic lobes, Fig. 43 d; 
the cleft passing into a shallow groove on the ventral surface which 
leads to the mouth m. The posterior extremity expands to form 
the caudal disc, ¢ d. 
This organ is convex above and concave below, its broadest 
part being near its junction with the body. In the centre of its 
ventral aspect two hooks, %, 4, closely resembling fish hooks, are 
placed back to back, the points being directed forwards and slightly 
downward, each point resting in the centre of a crescentic fold of 
VOL. III. 
