AVIAN CESTODES. 



599 



contents up to the margin of the water- vascular tube, occasionally 

 crumpling up the latter before it. Nevertheless, the more dilated 

 region is still distinguishable as the true receptaculum seminis. 

 It is evident, therefore, that the difierences apjDai^ently shown 

 between species in the vagina must be handled with care. I 

 may add tliat in fully mature proglottids the vagina appears 

 to be continued onwards bej'ond its junction vvith the other 

 tubes of the female system. This may be merely a burst, 

 though in some cases it has a tubular character. It is here, 

 I assume, that fertilization occurs. 



Text-figure 6. 



Ripe ova enclosed in capsules. 



o. Capsule containing ovum. sp. Part of vagina gorged with sperm, t. Remains 

 of a testes closely adpressed to an egg-capsule, tlie nuclei in the walls of which 

 are represented. 



The uterus in the genus Davcdnea is never a conspicuous 

 structure and never, when it exists, does it persist long. It is, 

 however, too much to say — as does Ransom * — that '' a definite 

 functional uterus is not developed." For in D. aruensis Fuhr- 

 mann t has described a uterus Avith a lining of cells and con- 

 taining ripe ova, which utei'us, however, rapidly disappears. The 

 same appears to be the case with D. microsGoleclna and D. corvina, 



* " The Tajnoid Cestodes of North American Birds. 

 No. 69, 1909, p. 14. 

 f Nova Guinea, vol. ix. Zoologic, Livr. 3, p. 169. 



Bull. U.S. Nat. Mus. 



