348 
BULLETIN OF THE UNITED STATES FISH COMMISSION, 
and composed of fine fibers, presumably contractile tissue, it may also function as an i 
ejaculatory duct. The vas deferens joins this from the posterior side. The cirrus is |i 
apparently iuvaginated by means of numerous retractor fibers, which are inserted on i 
the inner wall of the bulb and to the cirrus (Fig. 25, a). The testes are oval granular t 
bodies lying in the central core rather towards the margins (Fig. 32, t). They com- 
municate with the median vas deferens by means of minute ducts. 
The vagina opens near the cirrus, posteriorly to and a little to one side of it. It 
pursues a somewhat tortuous course posteriorly, apparently reaching the ovary on its ; 
dorsal side; near its beginning it expands into a seminal receptacle (Fig. 26.) The i 
ovary (Figs. 27, 33) appears to be a single mass of nucleated cells lying near the 
posterior edge of the segment and towards the ventral side, near the ventral layer of 
longitudinal muscles. Its longest diameter is transverse to the longitudinal axis of ( 
the segment. The shell gland, as I have made it out, lies near the ovary, somewhat t 
posteriorly on its dorsal side (Fig. 33, s g). The uterus is a very voluminous organ be- | 
ginuiug on the dorso-posterior side of the ovary and lying in broad folds rather toward 1; 
the dorsal side of the segment, the folds extending some distance on either side of the li 
median line aud occupying nearly the. entire length of the segment (Figs. 27, 28, 33). , 
Its caliber is much larger than the diameter of a single ovum. In the older segments ;; 
the walls of the uterus apparently give way, since the ova in them are seen to be in i 
masses in the central part of the strobile. (Fig. 24.) 
There is no indication that the segments separate in any other way than in long ' 
chains when mature. 
Sections made parallel with the lateral faces of the strobile show a small pore lying 
a short distance back ot the genital apertures and on the same side, i. e., the ventral (ij 
side of the strobile. This is apparently the external orifice of the uterus from which i' 
ova may be discharged. 
The ova are rather large, about 0.07 millimeter in length and 0.035 millimeter in i 
breadth. The walls are thin and usually collapsed in alcoholic specimens on one side, ; 
so that, in mounted specimens, the ova appear to be bowl-shape. They are of an 
amber color, do not stain readily, aud their contents are granular. They lie in some- 
what transversely parallel clusters along the median line, the masses of ova occupying 
a space approximately equal to one-third the breadth of the strobile. 
By counting the ova in a series of sections carried through a mass of ova iu a 
maturing segment, it was estimated that the segment contained 2,300 ova. The frag- 
ments from the intestines of one of these pelicans contained approximately over 2,000 ' 
segments. This would make 4,600,000 eggs from this strobile. This estimate does ; 
not include the ova in the attenuated fragments, which would probably yield as many 
more. These numbers are only approximations, but they probably are far below the 
actual numbers. It would be much within the bounds of probability to say that for 
each pelican on Yellowstone Lake in any season there are 5,000,000 eggs of Bibothriwn 
cordiceps discharged into the waters of the lake, under such conditions that make it 
probable that a small percentage of them eventually obtain lodgment in their proper 
intermediate host, the trout. 
V.— REMARKS ON CESTODS. 
During my sojourn at the hotel on Yellowstone Lake, at which time 1 met several 
tourists and others from various parts of the country, from England, and from France, 
