52 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
tion of which usually projects a greater or less distance into the follow- 
ing or third part, and always contains the nucleus. These two parts 
together have been called by Leidy the “head.” Thirdly, the posterior 
part, to which Leidy gave the name of “ body.” 
I begin with the anterior region, which I have found to be of rather 
complicated structure. To aid in the description, I have made sev- 
eral large semi-diagrammatic sketches (Plate 2, Figs. 7, 8, 11, 12, 17). 
Figures 7 and 8 are intended to represent sections not thicker than the 
space between two successive longitudinal rows of cilia. 
The nipple-like part of Trichonympha is, as the name which I have 
given it implies, a conical, more or less elongated protuberance at the 
front end of the parasite. According to its state of contraction it is 
one half, two thirds, or even more than two thirds, as thick at its base 
as it is long. The anterior end is evenly rounded or sometimes more 
pointed. Seen in profile its outline at the posterior end usually passes 
gradually into that of the middle part, but at times it appears sharply 
separated from this part by a deep constriction. Deep focusing and 
especially longitudinal sections show that the separation is more com- 
plete than superficial focusing would lead one to suppose. 
The “nipple” consists of a cylindrical, or slightly tapering, rod-like 
axis (Plate 2, Figs. 7, 8, 18, ax.), composed of finely granular proto- 
plasm, and one or more enveloping layers unlike in structure. The 
anterior end of the axial rod is expanded into a knob-like enlargement 
(Figs. 7, 8, tub.), the anterior surface of which has a conical (Fig. 7), or 
more commonly a hemispherical (Fig. 8) form. The rod is narrowest, 
a little in front of its middle, and thence increases in thickness very 
gradually both toward the knob and toward the “bell.” The protoplasm 
of the axial rod is continuous behind with the granular protoplasm 
which occupies the axis of the “bell,” and its surface appears to be 
differentiated into a thin membrane. This protoplasmic axial rod is 
surrounded by two, and possibly sometimes by three, well differentiated 
layers of formed substance (Fig. 7, st, & y Vig. 6, By. Bae is 
The middle layer often appears as though caused by an accidental 
separation between the outer and inner layers, but it is of so common 
occurrence that I do not feel able to declare positively that it is merely 
an artificially produced space. 
The anterior extremity of Trichonympha terminates in a colorless 
translucent cuticular cap (Figs. 7, 8, pil.), which stains only slightly at 
most, and frequently not at all. The centre of the cap covers the an- 
terior expanded end (tub.) of the rod-like protoplasmic core, and its 
