porter: trichonympha. 61 



scattered irregularly, apparently without relation to the contractile cords 

 of the body-wall. The young, as we shall see later, are provided with 

 a coat of abundant cilia uniformly distributed. 



The body-wall is not without further differentiation, for at regular 

 intervals it is marked by darker lines, which have the appearance of 

 thickenings of the wall, or of separate cord-like structures applied to 

 its inner surface. These are really contractile cords, which arise at the 

 knob-like structure of the anterior tip of the parasite where it joins the 

 peduncle. These cords are usually grouped together at the anterior 

 end of the body, so that a portion of the surface is quite bare of them 

 (Plate 4, Fig. 51a), They pass backward in a slightly spiral direction 

 (Iseotropic), leaving between one another equal spaces. As a rule, each 

 cord can be traced to the posterior extremity of the animal, and tlience 

 hack again on the opposite side of the animal to the anterior end ; but 

 sometimes the cords apparently terminate in cup-like depressions in the 

 body-wall, which resemble pock-marks, being outlined by coarse granu- 

 lar protoplasmic rings (Fig. 51, ann.). The cords are frequently so 

 superficial that in profile views of tlie animalcule they are seen to cause 

 the sui'face to project in the form of ridges. In some individuals there 

 is to be seen in the middle of the space between two successive cords 

 another and much finer line (Plate 4, Figs. 47, 54) running parallel 

 with them. This narrower line or cord is apparently embedded in a 

 more or less clear homogeneous substance, while the larger cords are 

 surrounded by coarse granular protoplasm. In other cases the larger 

 cords occupy the clear areas, and midway between them are sharply 

 marked lines of coarsely granular protoplasm, which stains more deeply 

 than the rest of the protoplasm (Fig. 51). 



In living specimens these cords keep up an incessant undulatory 

 motion, producing an effect which very closely resembles bands of 

 vibrating cilia The body of the adult, however, is generally quite bare 

 of cilia, but when it is ciliated, the cilia are, as I have said, scattered 

 promiscuously over the body, irrespective of the contractile cords. 



The contents of the sac-like body are finely and rather uniformly 

 granular, and not very thick or viscid, and there are appearances of 

 vacuolation in them. 



The nucleus of Pyrsonympha is a large pear-shaped or sometimes 

 oval body, generally situated at about one fourth or one third of the 

 distance from the anterior or attached end to the posterior end, and its 

 more pointed extremity is turned toward the attached end of the animal- 

 cule. It always contains a nucleolus (Plate 4, Fig. 47, 7ill.) at its larger 



VOL. XXXI. — NO. 3. 2 



