CONSTITUTION AND DEVELOPMBNT OF TERMITES. 51 



forms a single turn, it is easy to see that there are four, but 

 I cannot say that this number is constant in all individuals. 

 They are delicate in some and thicker in other examples. 



Lastly, as in Trichomonas^ a rod extends backwards from 

 the anterior extremity without being strictly axial ; it is ex- 

 tremely elastic, and appears to be bent by the rapid sinuations 

 of the body. 



Either or both extremities or the entire surface may also be 

 furnished with appendages which may be taken at first sight 

 for flagella, as has been done by Leidy. But after much 

 hesitation I have satisfied myself that they are parasitic 

 Spirilla, such as occur free in the intestinal contents of Ter- 

 mitidse. Their shape, size, inconstant presence, and irregular 

 distribution all justify this statement. 



VI. 



Pyrsonympha flagellata, Grassi. (PI. 20, figs. 18 — 20.) 

 ' Atti Ace. Lincei,' (5), i^ p. 36. 



This and the following form are assigned to a new family, 

 the Pyrsonymphidse, characterised by the body covered with 

 flagella, disposed more or less exactly in spiral lines, the 

 situation of the nucleus towards the anterior extremity, the 

 absence of a paranucleus, mouth and contractile vacuoles, 

 and lastly by the elliptic mouaxial body, with antero-posterior 

 asymmetry, moving, at least as a rule, in a helicoid path. 

 In the family I distinguish two genera, each with a single 

 species: Pyrsonympha flagellata, Grassi; and Holo- 

 mastigotes elougatum, Grassi. Leidy considers these 

 forms to be young Trichonymphse, a view I absolutely 

 reject. 



Pyrsonympha flagellata, which will first be dealt with 

 in detail, is subelliptical, and may measure as much as 98 ^u in 

 the major and 40 /z in the minor axis. The anterior extremity 

 terminates in a more or less evident papilla ; the posterior is 

 variable, and may be rounded or produced, &c. : it probably 

 serves for ingestion and elimination, as in Trichony mpha. 

 Nutrition is effected as in that genus. 



