T^NIOID CESTODES OF NOETH AMERICAN BIRDS. 17 



tions of the segment within the inner field. As in Davainea rhyn- 

 chota^ on the ri^ht-hand side this mass extends nearly to the anterior 

 border of the segment; on the left-hand (pore) side it is limited to 

 the posterior two-thirds. The vas deferens (fig. 7, v. def.) forms a 

 mass of coils in the anterior third of the segment extending from the 

 median line to the base of the cirrus pouch. The cirrus pouch (figs. 

 7, 8, c. p.) is pyriform in shape, with thin outer muscular wall, as in 

 Davainea rhynchota. It is, however, somewhat smaller in the present 

 species, measuring 90 to 100/x in length by 45 to 50/^ in diameter in 

 its widest portion. The arrangement in the pouch of the vas def- 

 erens and cirrus is similar to that in the other species. The cirrus is 

 without apparent spines, and measures in the retracted condition 

 about 50/x, in length by 2 to 4/x in diameter. 



cap.^ 



Pig. 8. — Davainea comitata: Geavid segment, ventral view, cap.. Egg capsules. 

 c. p., CiKEtJS POUCH, vag., Vagina. 



Female organs. — The vaginal opening is immediately posterior of 

 the male opening. The vagina and seminal receptacle are in this 

 form similar to those of Davainea rhynchota^ with the exception that 

 the vagina for a distance of 25/* from the genital pore is constricted, 

 and this constricted portion is surrounded by a bulbous sphincter. 



The ovary (fig. 7, o^y.), located as in Davainea rhynchota., is similar 

 in shape, lobulation, etc., and measures about 200/i in width at its 

 maximum of development. 



Posterior and ventral of the ovary is the yolk gland (fig. 7, y. g.) 

 100 to 130/x in diameter, and dorsal and anterior of the latter is the 

 small shell gland, 50/x in diameter. 



In the gravid segment the eggs are grouped 6 to 12 together m Qgg 



capsules (fig. 8, cap.)., measuring 80 to 90/^ in diameter. From 40 to 



50 capsules are visible from a surface view of the segment. They are 



confined to the medullary portion of the segment inside the inner 



3264— Bull. 69—09 2 



