ON PENNELLA BALZANOPTERZ. 423 
the cesophageal ganglia. From cells of this character being seen so frequently 
in the transverse sections, it was clear that a chain of ganglia extended longitudinally 
along the ventral aspect of the thoracic segment of the parasite, immediately internal 
to the chitinous envelope, and that from the ganglia nerves could readily be 
distributed to the wall of the adjoining parts of the alimentary canal. 
In transverse sections through the genito-abdominal segment collections of cells 
were seen immediately internal to the pigmented lining of the ventral part of the wall 
of chitin. They were arranged in a crescentic row, which followed the curvature of the 
wall, and the concavity of the crescent was directed towards the cement ducts, but was 
separated from them by a definite interval. The cells were nucleated, the cell-plasm 
was granulated, and two or three times greater in amount than the nucleus, which, 
again, was as big or even somewhat larger than the leucocytes, so abundant in the 
lateral mesenteries of the alimentary canal. Some of the cells were globular, others 
were elongated and rounded at the ends; occasionally I saw a multipolar cell, or one 
with a single pole, and frequently the cells were fusiform, with attenuated poles. From 
the position of the groups of cells in relation to the ventral wall of the parasite, and 
from their size and general character, | am of opinion that they form the abdominal 
chain of the nervous axis, and are engaged in the innervation of the organs contained 
in the genito-abdominal segment. 
In many of the sections a cell was situated beyond the termination of each horn of the 
erescent, which was greatly elongated, and its outer pole was prolonged as far as the 
wall of the cement duct, which protruded a pointed process to meet it. In some 
sections I observed that this pole bifurcated, and its limbs embraced and were prolonged 
into the wall of the cement duct. This cell was placed at the side of the ventral space 
and seemed to be in its wall. 
PENNATE APPENDAGES. 
These appendages, which constituted one of the most characteristic features of the 
genus, grew from the ventral surface of the terminal caudate segment of the abdomen, 
whilst an occasional one sprang from the sides of the genito-abdominal segment near 
the genital openings. They formed a closely-set brush-like arrangement, the bristles 
of which varied in length and projected from 4 to 7 mm. from the base of their 
attachment, which was continuous with the wall of the segment, and had the character 
of a papillary outgrowth of the wall. Branches arose from the stunted basal papille, 
and these almost immediately again divided, so that from six to ten secondary branches 
might proceed from a common stem. Lach branch had a pigmented core, inclosed in a 
translucent wall of chitin (Pl. I. fig. 4). 
In sections made through the caudate segment the knife sometimes passed through 
the chitinous wall at the spot where the base of a papilla sprang from it (fig. 18). 
The chitin of the segment was prolonged into the wall of the bristles, and the 
pigmented membrane lining the wall of the segment was continued directly into their 
