108 ILUNOIS BIOLOGICAL MONOGRAPHS [108 



DESCRIPTION OF PLATE 



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



X 80. 

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



genitalia. X 80. 

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



worm; U, lateral lappets. X 80. 

 Fig. 41. — Immature Cercaria flabelliformis within cj'st. X 54. 

 Fig. 42. — Cercaria flabelliformis; yoimg redia, detailing the excretory chaimels 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 yoimg daughter redia, showing 



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

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



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



P, G, longitudinal splitting of chromosomes at equatorial plate; H, 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-ov\mi, with polar body degenerating; M, metaphase of a 



somatic cell in process of division. X 1620. 



