94 ILLINOIS BIOLOGICAL MONOGRAPHS [288 



EXPLANATION OF PLATE 



Fig. 41. — Mesostoma angulare, lateral view, slightly compressed; X 35, 



Fig. 42. — Mesostoma simplex, slightly compressed; X 26. 



Fig. 43. — Eyes of Planaria maculata; X about 67. 



Fig. 44. — Eyes of Planaria maculata, camera lucida; X 67. 



Fig. 45. — Uterus of Mesostoma angulare, showing young worms and eggs just ready to hatch. 



X about 35. 

 Fig. 46. — Section thru fission plane of Stenostoma giganteum. Camera lucida; X SO. 

 Fig. 47. — Stenostoma glandiferum, dorsal view, slightly compressed; X about 90. 

 Fig. 48. — Stenostoma giganteum, lateral view slightly compressed; X 60. 

 Fig. 49. — Head of Dalyellia dodgei, antero-dorsal view, showing elevated mouth; X about 70. 

 Fig. 50. — Head of Stenostoma leucops, pharynx closed; X about 67. 

 Fig. 51. — ^Head of Stenostoma leucops, pharynx open; X about 67. 

 Fig. 52. — Nematocyst of Microstoma caudatum; X about 850. 

 Fig. 53. — Lateral view of head of Microstoma caudatum; X about 67. 

 Fig. 54. — Strongylosioma rosaceum, lateral view, slightly compressed; X about 50. 

 Fig. 55. — Transverse section, Mesostoma angulare, showing folds of body wall. Camera 



lucida; X 170. 

 Fig. 56. — Ventral view of head of Microstoma caudatum; X about 67. 



