Explanation of Plate I. 



Dissotreina papillatum. 



Fig. 1. An entire worm viewed from the ventral side, to show the principal organs 

 From a total mount, x 45 diam. 



Fig. 2. An entire worm viewed from the dorsal side, to show the nervous and ex- 

 cretory systems. X 45 diam. 



Fig. 3. A sagittal section of the worm, x 33 diam. 



Fig. 4. The genital organs with the exclusion of the vitellarium ; dorsal view. X125 

 diam. 



Fig. 5. An egg shell in three different aspects respectively at right angles to one 

 another. X 383 diam. 



Abbreviations. 



ac acetabulum. 



br brain. 



eg penis gland. 



co intestinal cœcum. 



dg dermal gland. 



ej ejaculatory duct. 



ex excretory pore. 



gm shell gland. 



gp genital pore. 



ic insemination chamber. 



lc Laurer's canal. 



m mouth. 



mt metraterm. 



ov ovary. 



pe penis. 



pg prostate gland. 



ph pharynx. 



pp prepharynx. 



ps penis sac. 



rs seminal receptacle. 



su oral sucker. 



sv seminal vesicle. 



t testis. 



ut uterus. 



ves excretory vesicle. 



vit vitellarium. 



yd yolk duct. 



yr yolk reservoir. 



