36 ILLINOIS BIOLOGICAL MONOGRAPHS [386 



grooves between the suckers, the dorsal and ventral grooves being the 

 deepest. All four fade out before reaching the apex. The very promi- 

 nent suckers face anterolaterad at an angle of about 45 degrees from 

 the axis of the worm. The mouths of the suckers are from 25 to 40//. 

 in diameter and the cavities are 70 to 90//, deep. The muscular wall of 

 the sucker is from 25 to 50//, thick. 



There is one set of reproductive organs to the proglottid, these 

 alternating with practically perfect regularitj^ from right to left; in a 

 dozen worms examined only three cases were found of two adjacent 

 proglottids with pores on the same side. The anlagen of the female 

 glands can be made out in the first proglottid. Testes are to be recog- 

 nized in the 15th and eggs pass into the uterus in the 40th. The 

 genital cloaca presents an unusual appearance. It is clearly divisible 

 into two parts, a lateral and a median. The lateral is an unusually 

 large structure varying in shape in different specimens probably on 

 account of contraction from nearly globular to angular, being even 

 acutely angular at its inner end. The pouch has a length of about 140//, 

 and a breadth of about 85//.. The anlage of this structure can be made 

 out in about the 20th proglottid as a group of cells that stain deeply. 

 Soon afterwards a mass of substance not distinguishable from the cuti- 

 cula can be made out in it near the lateral margin. A lumen appears 

 which increases in length mediad and then expands. Just before sexual 

 maturity the cuticula of the outer body wall is broken through, and the 

 cavity of the pocket becomes continuous with the outer surface. The 

 pouch immediately turns inside out, projecting abruptly in some cases 

 for more than 200//, from the margin. Fifteen or twenty proglottids 

 farther back it is again retraced to remain thus to the end. In its 

 fully developed stage the cuticula and wall of the pocket are directly 

 continuous with the cortical layer and not distinguishable from it. 

 Mediad of this and communicating with it is a second small pocket. 

 It is rather small and is expanded at its inner end to embrace the end 

 of the cirrus pouch. The vagina opens into its anterior border. Gen- 

 erally, the median end of the cloaca lies mediad of the longitudinal 

 excretory ducts. 



An unexpected condition was found in the position of the vagina 

 and cirrus pouch with respect to each other and to the nerve and 

 excretory trunks. When the pouch and vagina are on the right margin 

 of the strobila they cross the excretory ducts dorsally ; but when on the 

 left, in two individuals out of ten studied, they more often cross the 

 excretory ducts ventrally. In these two individuals out of 19 proglot- 

 tids which had the pores on the left margin ten had the genital ducts 

 ventral. Thus some proglottids have an arrangement that is charac- 



