68 ILLINOIS BIOLOGICAL MONOGRAPHS [356 



to C. americanus in that these wings also pass forward from the isthmus — but 

 only halfway along the sides of the uterus — and that the median region of the 

 latter is spherical and somewhat larger than the lateral portions. From the 

 anterodorsal aspect of this enlargement, which has a diameter of about 0.1mm., 

 the oviduct arises as described and figured for B. nylandicus. The diameter of 

 the oocapt is about 25/x, while that of the oviduct beyond its point of union 

 with the spermiduct is from 15 to 20^. The common vitelUne duct, formed by 

 the union close within the ventral musculature of a right and left duct, has a 

 diameter of 30jLt when filled with the yolk cells. The whole of the common 

 duct, 0.12mm. in length, acts as a vitelline reservoir, while the right and left 

 ducts usually contain a good deal of yelk close to their junction. As in B. 

 nylandicus the vitelline follicles are arranged in two lateral fields in the cortical 

 parenchyma, which are not only so restricted as to leave %\'ide median areas 

 free of them dorsally and ventrally but are continuous at the margins of the 

 strobila as well as from proglottis to proglottis. Like the testes they are spheri- 

 cal in shape, closely arranged, and have maximum diameters of 60^. The 

 shell-gland, located just beyond the point of union of the common vitelline duct 

 with the oviduct, is so weakly developed that it is all but absent. The opening 

 of the common vitelline duct into the oviduct was not found to be "from the 

 right side" as in B. nylandicus but irregularly from either side. Nor was there 

 seen any distinct enlargem.ent of the oviduct in the region of the ootype. 



The first portion of the uterus is very thin-walled, and, especially when free 

 of eggs, quite distinct from the distal portion which attains a diameter of 0.25 

 mm. The whole duct is so voluminous when filled \vith eggs that it occupies 

 ahnost the whole of the mxedullary region of the proglottis and hence more than 

 one-third of the transverse diameter and closely approximates that of the 

 proglottides ahead and behind, thus crowding the other organs ahnost to the 

 point of obliteration — and this in spite of the fact that its coils, mostly ar- 

 ranged in the sagittal direction, are very close together. The distal end of the 

 duct gradually narrows dowoi in passing ventrally to a diameter of from 35 to 

 45^i as it pierces the ventral musculature to open ahead of the vagina as above 

 mentioned. No special enlargement of the tube just before its opening, such 

 as was described for B. nylandicus is present in this form; but a considerable 

 length of the proximal portion of the duct is surrounded by glandular cells 

 quite similar to those of C. americanus (cf. p. 61). 



The maximum dimensions of the eggs are 36 by 24/x as compared to 40 by 

 25/1 in B. nylandicus. 



As the above description indicates, this form comes closest to B. nylandicus 

 Schneider, but it diflfers from that species in the followng important points: 

 It is considerably larger; the cuticula lining the bothria is the same as that 

 covering the general surface cf the strobila; the number and arrangement of 

 the excretory vessels are quite different; the structure of the nervous system 

 especially anteriorly is radically different; there are more than twice as many 

 sets of genitalia; there are no gland-like cells just outside of the cirrus-sac; 

 the vagina is expanded proximally into an elongated seminal vesicle; the open- 



