M. V. Lebour 
9 
The fish in question was spotted at infrequent intervals dorsally, some 
spots being below the lateral line and more above it, many occurring 
near and on the fins. A fair number of cysts were found in the muscles 
below the skin and even here there was a small amount of pigment 
present. The fish was quite healthy and seemed not at all incon¬ 
venienced by the cysts. The skin was quite clean and to a casual 
observer the spots might have seemed natural to the fish. 
From its habit of attracting pigment I propose for this worm the 
name Cercaria chromatophila, 
Cercaria chromatophila sp. inq. The cyst ’is oval and measures 
0’36 mm. x 0'2G mm. which is very much the same size as Williamson’s 
cysts (1911). Round it is deposited the blackish-brown pigment either 
completely covering it or leaving a small area on the outside uncovered. 
The pigment is arranged in closely aggregated star-like masses close 
together near the cyst and gradually dwindling as they get farther away 
from it (Plate I, fig. 9). A fibrous covering containing the pigment 
can be removed from the cyst by careful manipulation with needles and 
the worm is then seen coiled up inside. The cyst is formed of two 
coats both colourless and transparent, the first thick and extremely 
tough and elastic, the second, immediately internal to it and closely 
pressed to its walls, is very thin and easily ruptured. Great difficulty 
was experienced in opening the cyst without damaging the worm ; the 
most successful method was found to be to soak the cyst in normal salt 
solution for a day and then under a dissecting microscope prick it with 
a fine needle. By this means it was possible to get the worm to emerge 
still alive (figs. 7-8). 
Fully extended it measures 0 70 mm. in length, the greatest breadth 
being 0'24 mm. at the anterior third of the body which is pointed 
at each end but more blunt anteriorly, colourless and transparent. 
It is covered completely with small spines which dwindle posteriorly 
although they do not entirely disappear. 
The oral sucker is circular with a circular aperture at the extreme 
anterior end. It measures 0 06 mm. across, the aperture being 0’03 mm. 
across. A very small prepharynx O'Ol mm. in length leads to a broad 
and muscular pharynx 0'03 mm. long and this leads to the oesophagus 
0‘03 mm. long which branches into two long caeca which are narrow and 
bend inwards in front of the ventral sucker, curve outwards agfain and 
inwards with the tapering of the body and end at the extreme posterior- 
end. Inside the intestine are irumerous colourless refractive granules. 
The ventral sucker is situated very far back at the junction between 
