OF THE NEMATOIDS, PARASITIC AND FREE. 637 



moves ; c, permanent rigid shaft of spear ; d, permanent spear itself lodged 

 in substance of wall of oesophagus ; e, e, two longitudinal contractile bands 

 destined to move anterior portion of oesophagus and protrude spear ; f, f, 

 retinacula, binding these bands to parietal muscles ; h, h, integumental pores. 



Fig. 4. Portion of posterior extremity of same opposite the region where intestinal canal 

 becomes narrowed (a) : — b, b, thick chitinous portion of integument ; c, c, 

 lateral integumental channels through same ; d, d, lateral bands seen in 

 outline. 



Fig. 5. Portion of oesophagus of same : — a, lumen ; b, b, hyaline cells from oesophageal 

 walls. 



Fig. 6. Four of hepatic cells from walls of intestine of same, showing granular contents 

 only, in the form of dark-coloured, highly-refractive particles. 



Fig. 7. Group of glandular cells from surface of muscles of same. 



Fig. 8. Three spermatic cells of same as they are most frequently seen. 



Fig. 9. Later stage of same, more rarely met with, in form of elongated spindle-shaped 

 filaments. 



Fig. 10. Two hepatic cells of JDorylaimiis muscorum, showing in each a homogeneous, 

 central, nuclear body in addition to light-coloured particles. 



Fig. 11. Terminal portion of oesophagus of Bhabditis marina, showing simple valvular 

 apparatus closed. 



Fig. 12. Same, valvular apparatus open. 



Fig. 13. Motory spermatozoa of same species. 



Fig. 14. Anterior extremity of Plectus parietinm highly magnified, ventral aspect : — 

 a, a, lateral, circular, integumental spaces, probably having minute central 

 apertures in commimication with transparent flexuous vessels {b, b) by means 

 of narrower and more rigid portions {b', b') ; c, mid- ventral pore in connexion 

 with d, the curved, twisted and somewhat rigid duct in connexion veith gland. 



Fig. 15. One uterine segment and ovarian tube of same species : — a, vulva ; b, uterus 

 filled with large spermatic (X) cells ; c, c, short thick ovarian tube containing 

 unimpregnated ova. 



Fig. 16. Bodies almost exactly resembling the spermatic corpuscles of fig. 27, though 

 smaller, which were found fiUing the whole cavity of the body of a specimen 

 of Plectus cirrhatus. 



Fig. 17. Anterior extremity of adult Tylenchm ( Vibrio) tritici, lateral aspect :—a, mid- 

 ventral pore, communicating with curved rigid duct (b) ; c, one of lateral 

 flexuous vessels ; d, pharyngeal spear ; e, mid-oesophageal muscular swelling. 



Fig. 18. Spermatozoa of same species in different stages of development. 



Fig. 19. Hyaline cells, such as completely fill all other\Adse unoccupied parts of the 



canty of the body of same species. 

 Fig. 20. Ventral gland of Tylenchm Davainii : — a, its distinct rigid duct ; b, very indis- 

 tinct terminal dilated portion. 



