132 ILLINOIS BIOLOGICAL MONOGRAPHS [420 



lateral fields continuous from proglottis to proglottis, but the latter are united 

 dorsally and ventrally between the sets of genitaUa by the largest which are 

 somewhat more numerous and irregularly arranged ventrally. The average 

 maximum depth, width and length, of the individual follicles are 70, 50, and 

 45^1, respectively, while the diameter of the smallest lateral follicles, more 

 nearly spherical in shape, is about 25^. Their number as calculated from sec- 

 tions averages from 800 to 1000 for each set of reproductive organs. The 

 shell-gland is situated dorsally and to one side of the median line, the beginning 

 of the uterine tube occupying the other side of the generative space. The latter 

 is here not so much a space enclosed by the ovaries as the region of union of the 

 proximal portions of the generative ducts. That part of the oviduct with which 

 the cells of the gland are connected is only about 60ju in length. Beyond the 

 Gotype the oviduct gradually enlarges as it passes to the other side to become the 

 uterine tube. Farther ventrally the comparatively large coils of the uterine 

 duct pass back to the same side again and occupy a space lateral to the cirrus- 

 sac, as mentioned above in connection with the vas deferens. Just beyond the 

 shell-gland, where the syncitial nature of its epithelium can be made out, the 

 oviduct has a diameter of 13/x. The uterus-sac is relatively large in this 

 species, spherical in shape and occupies one-third of the diameter of the proglot- 

 tis anteroposteriorly as well as laterally. This applies to proglottides in mod- 

 erate state of contraction, for in much relaxed ones it is somewhat elUpsoidal 

 in shape with its long axis in the median Une. The youngest uterus-sac which 

 was seen to contain eggs in the largest and most relaxed strobila at hand was 

 spherical and had a diameter of 0.15mm., while the largest of the same chain, 

 also spherical, was 0.50mm. in diameter. But even when they appear circular 

 in outline from a superficial view, they are not in reality spherical since they 

 lead off funnel-wise ventrally to the uterus-opening. The superficial aspects 

 of the latter have been already dealt with above, so that it will be necessary to 

 state here only that it has quite the same structure as that of B. scorpii, and 

 that the actual aperture when formed is irregularly circular in outline with a 

 transverse diameter of 60 to 85/x. The wall of the uterus-sac just within the 

 opening is in many cases broken up into numerous processes, evidently cuti- 

 cular in their nature, which protrude thru the aperture. 



The egg is ellipsoidal in shape during life, and from 62 to 66/x long by 42 to 

 45/1 wide. None were found to contain oncospheres, but only masses of cells 

 such as shown in figures 106 and 107, the smaller of which obviously represents 

 an earUer stage in the division of the latter. While most of these cells are yolk- 

 cells, the large one shown at one end of figure 106 is the undivided egg. The 

 granules of figure 107 are those resulting from the breaking down of the yolk- 

 ceUs. Eggs sectioned in the uterus-sac showed similar stages in development 

 and confirmed these statements. These measurements and drawings were 

 made on August 2, 1912, so that it is probable that the development of the 

 oncosphere is completed in autumn. 



Concerning the life-history of this species it may be said that many of the 

 earliest formed segments are lost long before they become sexually mature, 



