418 SIR WILLIAM TURNER 
needles, and stained with picrocarmine, delicate fibres were seen to lie between the cells 
and to emerge from the ganglia, which, from their association with the nerve cells, 
were obviously nerve fibres. Some were non-medullated ; others, again, apparently 
contained a medullary substance, which had aggregated into little clumps within 
the neurilemma. 
The mid-ventral object above referred to, when examined in relatively thick sections 
and under low magnification, seemed to be a solid cord-like body, lying mesially in the 
long axis of the head. It was situated between the ventral aspect of the ali- 
mentary canal and the inner surface of the ventral chitinous wall of the head. 
In longitudinal sections it was traced as high as the muscles of the head, the fibres of 
which arched above it, from their origin from the envelope of chitin to the side of the 
oral cleft. Its transverse diameter was greater than the antero-posterior, and it was 
bounded by a distinct capsule of fibrous tissue, which gave it a definite outline and 
differentiated it from the surrounding structures. The cesophageal ganglia were in 
relation to its sides, and in places even encroached on its ventral surface, and their 
upper ends were in the same transverse plane as the upper limit of its investing capsule. 
Below the ganglia it was bounded by the areolated tissue which was so abundant at 
and immediately below the arms. From its position it might have been taken for an 
axial nerve cord associated with the cesophageal ganglia, but no fibres could be 
detected in it, and it did not stain with carmine (fig. 8, V). 
When thin sections were examined with a Zeiss lens x 250 the capsule was seen to be 
lined by a layer of rounded cells ; in favourable sections they formed a continuous lining, 
but not unfrequently they were arranged in patches, separated by intervals. The cells 
were much smaller than the nuclei of the nerve cells in the adjoining ganglia, they were 
nucleated, and the cell-plasm was dimly granular. The material generally inclosed by 
the capsule had a eranular character, and, as a rule, showed no trace of structure, and 
was possibly a coagulated substance. Sometimes, however, nucleated cells of great 
translucency were interspersed in the granular material, and fatty-looking globules were 
occasionally present. 
In sections through the body of the parasite in the thoracic segment the corre-— 
sponding arrangement, interposed between the alimentary canal and the ventral 
wall of chitin, was the ventral mesial space, so that the mid-ventral object above 
described was obviously a prolongation upwards into the head of the ventral space 
of the ccelom. 
In some of the transverse sections through the parasite made a little above the 
attachment of the arms a special appearance was seen. It consisted in the presence 
of a band or column of chitin, almost circular in outline, lying in relation to the dorsal 
space and interposed between the cesophagus and the inner surface of the dorsal wall 
of the chitinous envelope, and apparently quite independent of it. It was difficult to 
give a satisfactory explanation of the part which the band played in the economy of 
the parasite (figs. 8, 10, Ch). 
