16 



BULLETIN 69, UNITED STATES NATIONAL MUSEUM, 



The suckers are oval, 115 to 135/^ wide by 160/x long, armed with 

 numerous hooklets (fig. Qa) 10/* and less in length, arranged in 

 diagonal rows on the border of the suckers, 16 to 18 in each row. 



The neck is of variable length up to 400/x,, and measures in width 

 from 200 to 300/x. 



The segments are similar in shape to those of Davainea rhynchota 

 and increase gradually in size toward the posterior end of the stro- 

 bila. In a strobila 45 mm. long the number of segments was ap- 

 proximately 175, of which the last 17 contained egg capsules. A 

 segment (No. 130) in the middle of the strobila measured 320/* in 

 length by 880/* in width, and a segment at the end of the strobila 

 measured 650/* in length by 1.6 mm. in breadth. In some cases the 

 gravid segments are equal in length and breadth. 



v.ex. 



l.n.-/ 



^vag. 



sem.' recept 



200a. 



Fig. 7. — Davainea comitata : Sexually mature segment, eeconstuuction from sec- 

 TioNSj ventral view. c. p., CiEEus POUCH, d. ex.. Dorsal excretory vessel. I. n.. 

 Nerve cokd. ov.. Ovary, sem. recept., Seminal receptacle, t.. Testicles, vag., 

 Vagina, v. dej., Vas deferens, v. ex.. Ventral excretory vessel, y. g.. Yolk 

 gland. 



The genital pores are unilateral on the left-hand margin of the 

 strobila, situated in abo.ut the middle of each segment. 



Internal anatomy. 



The nervous system, musculature, and excretory canals are ar- 

 ranged as in Davainea rhynchota^ and the relative location of the 

 reproductive organs is the same. 



Th ) vas deferens and vagina pass between the excretory canals and 

 dorsal of the nerve cord, as in the other species. 



Male reproductive organs. — The testicles (fig. 7, t.) number from 

 30 to 35, arranged in a mass occupying the lateral and posterior por- 



