80 ILLINOIS BIOLOGICAL MONOGRAPHS [200 



EXPLANATION OF PLATE 

 Gordius robustus 



Fig. 8. — ^Posterior end of male; end view, slightly ventral; free hand sketch from alcoholic 



specimen; X 20. 

 Fig. 9. — Six day specimen from 1 4; posterior end turned up and not shown; X 250. 

 Fig. 10. — Section thru sperm mass just posterior to anal opening of female; shows free area 



where spermatozoa have migrated into cloaca; X 250. 

 Fig. 11. — Six day specimen from I 4; large nuclei in anterior end of intestine; X 385. 

 Fig. 12. — Spermatozoa in anterior end of male in which the adult cuticula is not fully develop- 

 ed; X 800. 

 Fig. 13. — Spermatozoa from posterior end of same specimen as in Fig. 12; X 800. 

 Fig. 14. — Larva after prolonged free existence; side view; drawn in optical section from stained 



specimen cleared in oil of wintergreen; X 1200. 

 Fig. 15. — Eight day specimen from I 8; intestine with large nuclei at anterior end; cells in 



cephalic ganglion somewhat enlarged; X 190. 

 Fig. 16. — Adult cuticula; surface view, showing intersecting lines and light spots; drawn to 



scale from living specimen obtained from Mt. Vernon, Illinois; X 30. 

 Fig. 17. — Spermatozoa from seminal receptacle of female; X 800. 

 Fig. 18. — Mature spermatozoa from male; X 800. 

 Fig. 19. — Spermatozoa in section of adult male; X 800. 

 Fig. 20. — ^Larva just hatched; side view; drawn in optical section from stained specimen 



cleared in oil of wintergreen; X 1325. 

 Fig. 21. — Proboscis of free living larva; section; X 800. 

 Fig. 22. — ^Anterior tip of parasitic form, showing larval hooks; X 240. 

 Fig. 23. — Section just posterior to preceding; X 240. 

 Fig. 24. — Posterior end of white male, nearly adult; side view; X 25. 

 Fig. 25. — Posterior end of white female, nearly adult; semi transparent; side view; X 25. 

 Fig. 26. — ^Posterior end of adult female; dorsal view; drawn from alcoholic specimen; X 25. 



