THE PARASITES OF THE TERMITES. 437 



fragments of wood-fibres, vessels, and cellular tissue, derived from the food of the 

 host. Among these sometimes wood-fibres of considerable length may be observed, 

 as seen in Fig. 4. 



The anterior end of Pyrsonympha is conical, or may become more or less ob- 

 tusely rounded or truncated. The posterior broader extremity is usually rounded, 

 or more or less angular or acute. Often also it is more or less tapering, and 

 frequently somewhat acuminate. Sometimes, too, it appears terminated by a 

 caudal appendage of variable form and length, but this has seemed to me to be a 

 production resulting from change due to dissolution. 



The sides of the body exhibit undulating, longitudinal folds proceeding from 

 the narrower towards the broader extremity of the body, which accord with corre- 

 sponding movements of the surface. These are especially obvious along the 

 lateral outlines of the body. The folds pursue a more or less spiral course, and 

 from the translucency of the animals appear to decussate from opposite sides. 

 They become more pronounced with greater activity, and often they seemingly 

 terminate in a series of prominent points to one side of the broader extremity of 

 the body, as represented in Figs. 1-3. At other times their deeply waving and 

 spiral course gives the animal the appearance of a screw rotating on its axis, as 

 seen in Figs. 8-12, 



In my earlier observations on Pyrsonympha I supposed the undulatory move- 

 ments of the body were due to cils, though ordinarily these were not perceptible. 

 In very many of the swarms examined with the utmost scrutiny I failed to detect 

 these organs, especially in the large and more conspicuous forms as well as in 

 others of somewhat peculiar character. Whether examined in the fresh and most 

 active condition, in the decline of their power, or after the cessation of movements, 

 the Pyrsonympha appeared to be entirely destitute of cils, as represented in Figs. 

 1-4, 8-12. 



In some cases variable numbers of Pyrsonympha, especially smaller ones, but 

 not unfrequently also large individuals, appeared to be invested with cils, some- 

 times more or less obscurely, and at others quite distinctly, as seen in Figs. 5-7. 



In some later observations, in many swarms of Pyrsonympha, the greater pro- 

 portion or nearly all were distinctly invested with cils, as represented in Figs. 

 14-17. These were generally smaller than those which appeared to be entirely 

 destitute of cils, but otherwise seemed to be identical. Many presented the usual 

 clavate form, vigorously bending in zigzag, as in Fig. 14; others were more or 

 less fusiform, and actively writhing, as in Figs. 16, 17. Among them were vari- 



