82 ILLINOIS BIOLOGICAL MONOGRAPHS [202 



EXPLANATION OF PLATE 



Gordius robustus 



Fig. 27. — Anterior end of adult male; dorsal view, drawn from alcoholic specimen; X 25. 



Fig. 28. — Anterior end of female, Leidy collection of 1879; dorsal view; drawn from alcoholic 

 specimen; X 25. 



Fig. 29. — Section thru posterior end of young male, showing jimction of sperm ducts and 

 intestine; X 360, 



Fig. 30. — Male and female; early stage in process of mating; sketch from living specimens; 

 XIO. 



Fig. 31. — Male and female; just before discharge of sperm; X 10. 



Fig. 32. — Posterior end of adult male; ventral view; drawn from alcoholic specimen; X 40. 



Fig. 33. — End view of anterior end; drawn from alcoholic specimen; X 50. 



Fig. 34. — Posterior end of adult female; end view; drawn from alcoholic specimen; X 50. 



Fig. 35. — Early stage in the development of adult cuticula; X 480. 



Fig. 36. — Cross section thru base of fork of male; adult cuticula not completely formed; shows 

 canal passing from end of intestine to outlet in larval cuticula at tip of fork; X 120. 



Fig. 37. — Sagital section thru postcloacal ridge of young male; X 140. 



Fig. 38. — Structure of adult cuticula; X 440. 



