PORTER: TRICHONYMPHA. 59 
the longitudinal axis, their bodies changing form little or not at all. 
This rotation is undoubtedly due to the spiral arrangement of the 
cilia, but the constant motion of these organs makes it impossible to 
discover in living specimens what the arrangement of the cilia is. 
The bodies of these worm-like animalcules (Figs. 30-32, 37-39, 42-44) 
are invariably filled with great numbers of large protoplasmic granules ; 
this is not the case with any of the other parasites. 
It seems to me that the characters of this form are sufficiently definite 
and different from those of the other forms described to allow one to 
consider them the representatives of another species. 
2. Pyrsonympha vertens. 
Plate 3, Figs. 33, 34, 40, 413 Plate 4; Plate 5. 
Pyrsonympha in its mature state is much larger than Trichonympha. 
Either the parasites found in the vicinity of Cambridge attain a greater 
size than those studied by Leidy, or else this author failed to see the 
largest individuals, for the longest specimen seen by Leidy measured 
only 160 a, whereas the one which is shown in longitudinal section in 
Figure 33 (Plate 3) is 275 u long, exclusive of the peduncle ; this being 
a large, but not an exceptionally large individual. 
Pyrsonympha, like Trichonympha, evidently feeds on solid food, so 
that the question again confronts us, How does this food enter the 
body? Sometimes the whole posterior portion of the animalcule is 
filled with fragments of wood fibre (Fig. 34). These fragments are 
often of considerable size. I have seen, within the posterior part of 
the body, a single rectangular piece so large that it touched both sides 
of the body, and extended anteriorly almost to the nucleus. Surely, a 
mouth large enough to swallow such a portion of food must be recog- 
nizable; but I have been unable to discover any aperture whatsoever 
in the body-wall of the animal, 
Pyrsonympha is usually more or less club-shaped, the relative pro- 
portions of length and thickness, and the particular form, being of course 
dependent on the degree and nature of its contraction (Plate 3, Figs. 33, 
34, 40, 41; Plate 4, Figs. 45, 51, 53, 55). In the adult condition 
it appears always to be attached to the wall of the host’s intes- 
tine, a fact which Leidy, strangely enough, seems to have entirely over- 
looked. The attachment is by means of the narrower end, which is 
prolonged into a sort of homogeneous stalk or peduncle, having only a 
slender connection with the main portion of the parasite. The peduncle 
