52 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



tion of which usually projects a greater or less distauce iuto 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 

 pai't, 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-diagram matic 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 Trichonyaipha 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, hih?), the anterior surfice 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/, st.'" ; Fig. 8, st.', st", st.'"). 

 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 



