104

the latera ventral di cauliorchis being mor longitudin

curve ven

transverse

SURFAC marked b

the ventra

like papil the papill somewhat Genital

the juncti transverse

FIG. 73.

about 0.45 mm. in length. This slit, or slit-like depression, is at the vertex of a moderate, transversely elongate elevation, and represents the genital pore.

Acetabulum.-The acetabulum is large, and, as in the other forms of this group, it is in the caudal portion of the body. Its relatively small aperture is directed slightly ventrad on account of the curve of the body. Measurements taken from the projection of one sectioned specimen give 2.74 mm. as the greatest dorso-ventral and 3.10 mm. as the greatest transverse diameter of the acetabulum, with 0.34 mm. as the greatest verticle and about 0.50 mm. as the greatest transverse diameter of the acetabular aperture. The true aperture of the acetabulum is somewhat reduced in size by being

encroached upon by folds of the adjacent body surface, much as in the case of Paramphist. cauliorchis.

INTERNAL ANATOMY.

DIGESTIVE TRACT.-The cephalic pole is marked by an irregularly circular aperture, measuring in section 90μ by 120μ in diameter. This aperture leads into a shallow irregular cavity which gives entrance to the oral sucker. The latter is a large muscular organ, which in projection of one specimen measured 1.34 mm. in longitudinal axis, 0.98 mm. in greatest dorso-ventral diameter, and 1.26 mm. in greatest transverse diameter. The dorsal and ventral walls are thick, measuring 0.46 mm. and 0.50 mm. in thickness, respectively,

when measured in the greatest dorso-ventral diameter of the sagittal plane. Laterally these muscular plates are thinner and continuous one with the other. The organ is inclosed in a narrow space in the body parenchyma (figs. 74, 75), in which it is retained in position by attachments at its two poles and by dorsal and ventral mesenterium-like strands. The lumen of the sucker is a dorso-ventrally, very narrow, but transversely quite broad, cavity. In transverse sections it appears as a transverse slit lined by a thin cuticle-like layer, which is beset by short conical papilla; the latter are largest in the oral half of the lumen, become gradually smaller and more slender in the direction of the esophageal end, near which they disappear altogether. The esophagus springs from the caudal or basal aspect of the sucker, then describes a more or less well-marked U

shaped course with the base of the U ventrad. The caudal limb of the U is much the longer and is directed almost horizontally dorsad, having only a slight tilt caudad; it divides into the 2 intestinal ceca. These at first pass laterad with a tilt cephalad to a plane slightly above their plane of origin, describing at the same time a slight curve having its convexity dorsad. After approaching the ventro-lateral aspect of the body wall, each of the intestinal tubes bends caudad and describes a decidedly wavy, almost zigzag, course caudad, approximately parallel to the lateral body wall of the worm. The cecal extremities are directed ventrad close to the sides of the acetabulum and at about the level of the upper margin of the acetabular aperture. The lumen of the esophagus is lined by a cuticle-like layer continuous with that of the oral sucker, but terminating abruptly at the

point of origin of the ceca. The latter are lined by an epithelial cell layer.

GENITAL SYSTEM.-With the exception of the vitellaria, the genital organs are disposed in the intercecal space.

Male organs. The testes are in the equatorial zone of the worm, one laterad of the other, and separated by a moderate interspace. They are in separate but more or less overlapping testicular zones and fields (fig. 72). In both of two sectioned specimens the right testis was the more cephalad. In transverse sections the testes appear to be composed of numerous lobules suggesting a cauliflower-like appearance (fig. 78). From the external aspect of each testis there emerges a vas efferens, which tends at first cephalad, then dorsomediad, finally uniting with its fellow to form the vas deferens (fig. 72). The vas deferens is distinctly divisible into a vesicula, musculosa, prostatica, and ductus ejaculatorius. The vesicula is loosely but complexly coiled, thin walled, and but slightly dilated. It is succeeded by a complexly and somewhat more compactly coiled musculosa. The muscular walls of this portion of the vas deferens are well developed, but not nearly so much as in Paramphist.cauliorchis; measured at a favorable point the diameter of the duct was 0.24 mm., with a thickness of wall of 0.067 mm. There is in this, as in Paramphist. cauliorchis, a short intermediate segment or pars intermedia between the vesicula

FIG. 76.

and musculosa. This segment is muscular but of less diameter and both much thinner walled and of smaller caliber than the musculosa. The change from musculosa to prostatica is clearly marked by a change in the structure of the wall and by the appearance of a thin layer of cells which inclose this third portion of the vas deferens. The prostatica is not coiled, but pursues a direct course cephaloventrad. As it nears a prominent somewhat globular muscular mass, which incloses the terminal genital (copulatory) apparatus, the prostatic cells are lost, and the prostatica now continues as the ductus ejaculatorius. It penetrates this muscular mass in close relation to the dorsal aspect of the terminal portion of the uterus. This portion of the male duct is still of considerable caliber and thin walled, giving the impression of a vesicle, but after a very short course becomes abruptly reduced to a relatively very narrow and short canal, which is interpreted as opening with the terminal portion of the uterus into a minute slit-like space at the base of a minute genital papilla (fig. 75). The latter is pierced in its long axis by a very delicate canal, interpreted as the ductus hermaphro