414 SIR WILLIAM TURNER 
and came toa free end. It had a caudate appearance ; but as it contained the intestinal 
end of the alimentary canal, it should be regarded as the caudate segment of the 
abdomen. ‘The anal orifice was situated in a cleft at its free end. Its dorsal surface 
was marked by transverse constrictions, and from its ventral surface a number of 
bristle-like structures arose, which gave to the terminal part of the body the pennate 
character which has decided the generic name. 
CuHITINous Coat. 
The chitinous coat of the parasite was translucent, firm, and so tough as to turn 
the edge of the razor. It was for the most part homogeneous throughout its substance, 
but in places delicate lines, parallel to each other and to the plane of the surface, gave — 
it a laminated appearance, as if it had been formed by superposition of layers. It 
varied in thickness in different regions, as was seen both in longitudinal and transverse 
sections. In the head, this coat was about 4rd of a mm. thick, but at the origin of the © 
arms it was about $rds of a mm. In the arm itself the thickness varied in different parts. 
In proximity to the head it formed about 3rds of the diameter of a transverse section, in 
the middle of the arm about 4rd, and near the free end about 4. In the attenuated — 
thoracic region the proportion was about 4, in the genito-abdominal part it was less, 
and it was a little thinner on the ventral than on the dorsal aspect. In the pennated — 
abdomino-caudate segment it represented about 4rd of the transverse diameter of the 
parasite. 
On the outer surface of the chitinous envelope a layer of cuticle was present, which 
was usually closely adherent to the chitin, but in places it was partially detached, and 
had probably been drawn off in cuttimg the sections. When examined microscopically 
it was seen to be striated in a direction perpendicular to the plane of the surface ; 
higher magnification showed this appearance to be due to short columnar cells, which 
were arranged parallel to each other. In sections where the displaced cuticle had been 
turned over so as to expose its free surface, the broader ends of the columnar cells 
were seen to be at that surface, and by their close apposition to each other to forma — 
continuous layer. 
The chitinous wall was lined by a membrane, which in various localities, to be sub- — 
sequently referred to, was richly pigmented (figs. 17, 24, 26). 
In the papilla-like tubercles, in the parts of the head not occupied by the mnie 
in the thickened part of the body immediately below the head and in the arms, 
an areolated tissue was situated within the membranous lining of the wall of chitin. 
STRUCTURE OF THE Heap. 
The internal structure of the head was examined in a series of transverse and 
longitudinal sections from its summit to the base of attachment of the arms, The 
