234 



ILLINOIS BIOLOGICAL MONOGRAPHS 



[234 



2avity is deep. This head is 1.19 mm. broad, 0.60 mm. long, 0.935 mm. 

 thick. The comparative table which follows presents the data on the 

 head as secured by Barrois, Marotel, Schwarz, and the writer. 



The neck of the specimen observed by the writer measured about 

 5-8 mm. long by 0.980 mm. broad. Its limits could not readily be de- 

 termined in a glycerine preparation. Marotel states that the neck is 4 

 or 5 mm. long and 0.580 mm. broad at its narrowest place. Barrois and 

 Schwarz do not state its dimensions. The first proglottids are much 

 broader than -long. These increase in length more rapidly than in 

 breadth. Marotel (1899) states that at 20 mm. from the head the pro- 

 glottids measure 0.255 mm. long by 0.63 mm. broad ; at 25 mm. 0,65 by 

 0.65 mm. i. e., they are quadrate ; at 30 mm., 0.71 mm. long, 0.67 mm. 

 broad ; at 40 mm., 1.45 by 0.75 mm., and the last proglottids are 3 to 4 

 mm. long by 1.0 mm. broad. In material examined by the writer nearly 

 mature proglottids measure as much as 0.9 mm. broad by 0.55 mm. 

 long and mature proglottids about 0.85 mm. square or some of them 

 may be a little longer than broad. Ripe proglottids measure 2-3 mm. 

 long by 1.0-1.2 mm. in breadth. In some contracted regions of the 

 strobila the breadth may measure as much as 2.0 mm. 



The sexual aperture is irregularly alternating, situated in mature 

 proglottids at or slightly anterior to the middle of the margin. In ripe 

 proglottids it may be either anterior or posterior to the middle. Both 

 cirrus and vagina open into a common genital sinus which is very 

 shallow. The vagina lies anterior or posterior to the cirrus-pouch with 

 almost equal frequency. In ripe proglottids frequently and in mature 

 proglottids more rarely, the vagina may open dorsal to the cirrus- 

 pouch. 



The testes (Figs. 109, 110) number from 130 to 160 in the writer's 

 preparation and these numbers are also about the limits observed by 

 the other investigators. They measure from 0.026 to 0.037 mm. by 0.053 

 to 0.063 mm. in the writer's preparations. Others report them as measur- 



