108 ILLINOIS BIOLOGICAL MONOGRAPHS [108 



DESCRIPTION OF PLATE 



Fig. 38. — Cercaria flahellijormis; ventral view of worm freed from cyst; //, lateral lappets 



X 80. 

 Fig. 39. — Cercaria fiabelliformis; dorsal view, giving details of the excretory system and 



genitalia. X 80. 

 Fig. 40. — Cercaria flahellijormis; lateral view, showing suctorial cup in anterior portion of 



worm; II, lateral lappets. X 80. 

 Fig. 41. — Immature Cercaria fiahelliformis within cyst. X 54. 

 Fig. 42. — Cercaria flabelliforviis; young redia, detailing the excretory channels in the worm. 



X 54. 

 Fig. 43. — Cercaria flabelliformis ; redia showing paired salivary glands emptying into the 



oral pocket. X 54. 

 Fig. 44. — Cercaria flabelliformis; mid-frontal section thru young daughter redia in region of 



germinal cell maturation. X 330. 

 Fig. 45. — Cercaria flabelliformis; median frontal section thru young daughter redia, showing 



proliferation of germinal epithelium at posterior end of gut. X 330. 

 Fig. 46 a-m. — Cercaria flabelliformis rediae; maturation of parthenogenetic ova; A, resting 



cell; B, C, formation of spireme; D, division of spireme skein into eight chromosomes; E. 



F, G, longitudinal splitting of chromosomes at equatorial plate; fl', mitosis, with forma. 



tion of polar body and preparation of ovum for second mitosis; /, polar body almost 



constricted off, chromosome b excentric; /, ovum preparing for second division, polar 



body also dividing; K, cell cleavage, with precocious chromosomes bi, b2 excentric; 



L, first cleavage of a cercaria-ovum, with polar body degenerating; M, metaphase of a 



somatic cell in process of division. X 1620. 



