4291 PSEV DOPEY LLIDEA FROM FISHES— COOPER 141 



whole of the medulla dorsoventrally at these points. In mature proglottides 

 they have the same relative positions in the frontal plane, but are located in 

 the ventral one-half of the medulla, their transverse diameter being as much 

 as 50)u. In the scolex each expands opposite the edges of the terminal disc to 

 form a ganglion, which sends out a large branch to each of the two quadrants 

 of the disc on the same side, and connects with its fellow by a slightly narrower 

 commissure. 



Four main longitudinal excretory vessels maintain a constant course 

 thruout the anterior segments. These are arranged in two pairs, a more median 

 and a lateral, not in the same plane in the medulla. The members of the 

 latter are the larger and are situated at the sides of the median one-quarter 

 of the transverse diameter of the segment. All of these vessels are connected 

 at various levels by large branches to form an extensive plexus thruout the 

 medulla. In the posterior crowded segments, however, the main vessels 

 become lost in the plexus, altho here and there they seem to occupy their origi- 

 nal positions thru a few sections. Only two large vessels, probably the lateral 

 pair, giving off many branches of the same calibre, can be followed with cer- 

 tainty into the scolex. About half way to the summit of the terminal disc 

 they break up into a plexus which ramifies thruout the walls of the bothria. 

 The posterior end of the smallest strobila at hand showed the same sort of 

 communication of a terminal plexus with the exterior thru large side branches 

 and foramina secundaria as in B. scar pit. 



Linton (1889:457) described the reproductive organs in general in the 

 following words: "In alcohoUc specimens a dark median line will be noticed 

 extending from the posterior end to the middle or anterior third of the strobila. 

 This is due to the central* situated ovaries [uterus-sacs], which are crowded 

 with eggs. The genital apertures are lateral and may be traced in an irregular 

 zig-zag line on one side from about the anterior third of the body. In the 

 mature segments they are rendered obscure, if not wholly obUterated, by the 

 mass of eggs with which the center of the segment is filled," and later (1890: 

 729, 730) besides giving the external features, quoted above, stated that "The 

 reproductive apertures are near the median line on one of the lateral sides. 

 They are very close together and rather small. Each aperture represents a 

 pair of sexual organs, cirrus and vagina. Upon making a few longitudinal 

 sections on the lateral [dorsal] face which bears the reproductive apertures, 

 the small vaginal opening comes into view. It opens into the common aperture 

 from behind and near the surface. The large aperture continues into the cirrus- 

 bulb. ..." Linton correctly stated that the common genital openings are 

 arranged * in a zig-zag row" in the median Une, as shown in figure 73; but much 

 of this irregular lateral displacement in the mature proglottides would seem 

 to be due to lateral pressure exerted by other organs, probably the gorged 

 uterus-sacs or at least the uterine ducts, since in immature segments where 

 the cirrus-sacs are already well developed, they are almost exactly in the 

 median line. In sagittal sections the genital cloaca is seen to open to the 

 exterior at about the middle of the length of the very short mature proglottis 



