60 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 55. 



Fig. 59. — JIesoces- 

 toides lineatus. 

 Portion ofStro- 

 bila , showing ma- 

 ture segments. 

 Enlarged. Af- 

 ter Neumann, 

 1896. 



Specific diagnosis. — Mesocestoides: The head is 600 to 900 [i in 

 diameter, massive and somewhat flattened anteriorly. The rostellum 

 is rephiced by a slight central depression. The suckers are oval and 

 display a widely opened longitudinal aperture. The neck is com- 

 paratively short and thick. The strobila measures from 30 cm. to 

 2.5 meters, and shows a feebly reddish color along the median line. 

 The first segments are very short and indistinct. The 

 f ollow^ing segments become square, with slightly con- 

 vex lateral borders and with slightly prominent pos- 

 terior angles (fig. 59). Segments become mature in 

 the middle third of the strobila. The terminal seg- 

 ments measure 4 to 6 mm. long and 2 to 3 mm. wide, 

 are shaped like melon seeds and are swollen in the 

 median line by the ovoid uterine capsule filled with 

 eggs. The male genitalia develop first. 



Male genitalia. — Testes large and numerous (about 

 50) and scattered through the segment both median 

 and lateral of the longitudinal excretory canals. Vas 

 deferens describes numerous loops near the mid- dorsal 

 line to the anterior extremity of the segment, where 

 it turns abruptly and enters the cirrus pouch. The 

 cirrus pouch is in the anterior portion of the segment, is well de- 

 veloped and prominent, piriform, and with its posterior aperture 

 opening alternately, usually regularly but at times irregularly, a 

 little to the right and to the left of the median line (fig. 59). The 

 cirrus is from 50 pi, to 1 mm. long, swollen at its proximal extremity 

 and commonly found protruded in mature segments. 



Female genitalia. — The ovaries are located v^,^i_.__ 

 in the posterior fourth of the segment, and / \ '" 

 are irregularly spherical to oval. There are ; i , 

 two vitellaria which are partly posterior of / \\ :'_ 

 the ovaries and partly underneath the pos- 

 terior portion of the ovaries. The vagina ex- 

 tends anteriorly and then returns in a sinuous 

 curve posteriorly from the genital pore and 

 on the side of the median line opposite to the 

 cirrus pouch (fig. 60) ; it is without a re- 

 ceptaculum seminis. The uterus forms as an 

 elongate sac in the median line, and presents 

 anteriorly a curve to one side, the cirrus pouch always lying in 

 the concavity of this curve, and the curve being alternately, regularly 

 or irregularly, to the right or to the left (fig. 59). The posterior 

 dilation of the uterus transforms into an egg capsule, the remains 

 of the primitive uterus persisting as attached cord-like structures, 

 a short one posteriorly and a longer, sinuous one anteriorly. The 



il 



VV 



Fig. 60.— Mesocestoides unea- 

 Tus. Mature segment. En- 

 larged. After Neumann, 

 1896. 



