367] PSEUDOPHYLLIDEA FROM FISHES— COOPER 79 



especially in frontal sections of younger proglottides, since they are com- 

 paratively large and hence quite distinct. The shell-gland is a small compact 

 organ, about 11 5^ in width by 55/x in length, surrounding the oviduct just 

 beyond the entrance of the vitelline duct, or to be more exact, just beyond the 

 first turn taken by the latter in its return to the median line after passing 

 laterally, as above stated. It is thus situated ventrally and a short distance 

 from the median line. Beyond the shell-gland the oviduct continues as the 

 uterine duct which takes only a few dorsoventral turns near the median line 

 before emptying into the uterus-sac. The latter is formed in development 

 by the gradual enlargement dorsally of that portion of the duct which traverses 

 the cortical parenchyma on the ventral surface of the proglottis. Just before 

 eggs appear in the sac this part of the tube can be seen in transections as a 

 spindle-shaped dilatation, whose nucleated epithelial wall is surrounded by 

 a thick layer of nuclei, the whole being, however, not distinctly separated from 

 the proximal portion of the tube (the uterine duct of older stages) at a constric- 

 tion just within the transverse musculature. In proglottides farther ahead 

 this constriction is outside of the transverse muscles in the cortex; so that the 

 uterus-sac must be looked upon, then, as being formed by a gradual enlarge- 

 ment of the distal end of the uterus as it becomes filled with eggs and not as 

 a sac separated in the rudiments from the proximal uterine tract as in the 

 Ptychobothriidae. In one case where only 5 or 6 eggs appeared in the lumen 

 the uterus-sac had a diameter in frontal sections of 80.u; in the next segment 

 following it was enlarged in all directions, somewhat elliptical in outline, with 

 a diameter of 240/x; in the next still larger; and in the fourth somewhat pointed 

 anteriorly. From this region on it quickly enlarges until finally it forms a 

 capacious sac, as much as 1.0mm. in diameter, occupying in gravid proglottides 

 the whole of the dorsoventral diameter of the medulla and almost all of the 

 longitudinal and transverse diameters. In transverse sections it is almost 

 entire in outline, while in frontal sections it is divided into from .S to 8 large 

 irregularly shaped lobes or diverticula, the hindermost two of which enclose 

 the remainder of the ovary and the central connections of the reproductive 

 ducts, as above mentioned. Ventrally, the sac is funnel-shaped towards 

 the small opening which only appears when the proglottis becomes quite 

 gravid. Since the uterus-sacs, even the most gravid ones, are not situated 

 exactly in the median line but towards the margins bearing the genital cloacae, 

 the openings form " ... a zig-zag line of minute pores [which] traverses 

 the median region of one of the broad faces of the strobila, each pore being 

 near the middle of its segment." Linton correctly considered them to be 

 for the escape of the eggs. Anteriorly, where the uterus-sacs do not yet con- 

 tain eggs, these pores — in reality the ventral funnel-shaped portions of the 

 sacs — are located about 0.18mm. on each side of the median line, but posterior- 

 ly they are relatively much closer together, in fact almost exactly in the median 

 line. Furthermore, they are situated directly opposite or slightly behind the 

 level of the genital cloaca. The opening is formed by the rupture of the body 



