32 



ILLINOIS BIOLOGICAL MONOGRAPHS 



[382 



the vacuolated space surrounding the cirrus pouch. The fully devel- 

 oped uterine embryos are 14.5/* to 15.5/* in diameter. The inner embry- 

 onic membrane is 18/* to 20/* across; the length of the embryo plus the 

 pyriform body is 26.5/* to 29/*. The outer mebrane is 55 to 61/* in 

 diameter; the middle is loosefitting and irregular. 



The ventral excretory duct has a diameter of 45 to 75/*, and the 

 dorsal is about half this size. Both lie in approximately the same 

 dorsoventral plane. Near the distal end of the proglottid the ventral 

 duct turns and runs abruptly mediad for a distance of about 275/* 

 where it gives off the transverse commissure. Beyond the commissure 

 and therefore in the next proglottid the duct turns laterad not so 

 abruptly as before to regain its lateral position. Stiles records that he 

 has observed the dorsal duct in open communication with the trans- 

 verse commissure ; since this occurs also in 8. variabilis and S. anoplo- 

 cephaloides, it seems to be a common occurrence in the genus. 



Stiles in 1896 referred to this species five cestodes from a rabbit 

 (host species and locality not known), giving them the rank of a va- 

 riety with the name Bertia americana leporis. His description is very 

 unsatisfactory being based upon poorly preserved, unsectioned material. 

 In reading over carefully the description of the worms there does not 

 appear a single anatomical character upon which to justify giving 

 them the rank of a distinct variety. The cirrus is supposed to be 

 smooth ; but this conclusion is based upon extruded cirri, and as shown, 

 extruded cirri of the forms from the porcupines are usually if not 

 always smooth. The testes are stated to be probably fewer; but Stiles 

 is not certain as to the count and the difference moreover is not so 

 great as that between the extremes of the next species. The description 

 of the position of the genital pore is vague but implies a difference ; 

 yet his figures (Stiles 1896, PL X, Figs. 7, 14, and 15) are identical 

 for both. Some slight differences were observed in the first appearance 

 of the genital anlagen; but such appearances when based upon unsec- 

 tioned specimens and poor material, do not have any importance. No 

 other points of difference were brought out which could not be ac- 

 counted for as mere individual variations. There appears therefore to 

 be no evidence to justify giving these specimens the rank of variety. 



On the other hand there is very little evidence that these cestodes 

 rightly belong to this species, or even to the genus for that matter. 

 As will be shown in the succeeding paragraphs the supposedly homo- 

 geneous materials from the porcupine prove to be two distinct species. 

 Until something is known of them however they should not be given 

 separate recognition. 



