88 Maddox, on Parasites of the Common Haddock. 
cord are found studded with flattened bead-shaped bodies 
plainly visible to the unaided eye. Removing a portion of 
one of these nodulated nerves, placing it in water under the 
microscope if the fish have not been too long dead, these 
“ spheroidal bodies” of Monro are seen to be cysts, generally 
imbedded in and displacing the nerve structure, and con- 
taining a spinous parasite bent up, which in many cases can 
be seen to execute partial movements of revolution on an axis 
at right angles to its length. After removing the surrounding 
nerve fibres and exposing the cyst to more complete view, it 
is seen to contain besides the animal, a grumous fluid and 
numerous oily-looking globules, set in motion by the move- 
ments of the parasite. 
The cyst seems to be composed of a more or less compact 
substance, brownish in colour, especially by transmitted light, 
and lined by a softer but somewhat brittle substance, inter- 
nally having, as seen through the walls of the cyst, fissures in 
every direction. The cysts are of a very variable size ; some 
of the smaller not more than the -j-Aoth of an inch, others 
much larger, but the average may be taken as T -g-oths of an 
inch, more or less ovoid and flattened; some are, as in PI. VIII, 
fig. 6, double ; that is to say, when two cysts by the growth of 
the creature and expansion of the walls have met, the ad- 
joining walls are removed, and the two cysts form but -one 
cavity, and, as in the sketch, contain two parasites. This 
appearance is not very common. I have met with it twice. 
On careful examination of the cysts, both in situ and removed, 
I could find no aperture, nor under compression did the 
cysts rupture more easily in one direction than in another. 
These cysts are described by Mr. Goodsir as similar to the 
cysts of Cysticercus , as also to the cysts of Trichina spiralis 
Gymnorrhyncus horridus and a small Filaria inhabiting the 
livers of some fish. “ The cysts of all these worms have 
similar structures- to those of Cysticercus, namely, an external 
membrane composed of compressed cellular tissue, and an 
internal membrane containing absorbing cells, through which 
the contained animal obtains nourishment.” Mr. Goodsir 
cites the encysted Gymnorrhyncus found in the liver of the 
sunfish as an example, — the “ inner membrane of the cyst 
containing absorbent cells is covered anteriorly with a very 
thin layer only of the external membrane, so that it is enabled 
to absorb the nourishment from the external textures in great 
abundance, which thus enables the animal to move forward 
as well as obtain a supply of food.” Mr. Goodsir states that 
“ Professor Owen, in the description of a microscopic entozoon 
infesting the muscles of the human body, considered the cysts 
