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ILLINOIS BIOLOGICAL MONOGRAPHS 



[414 



posterior part is comparatively thick and slightly more convex ventrally than 

 dorsally. The strobila as a whole gradually enlarges from the former to the 

 latter. 



The following table gives the measurements of six of the largest specimens 

 at hand; all dimensions are given in millimeters. 



The cuticula is very thin, being only 3.5/i in thickness, and with the highest 

 magnifications is resolved into two layers — an outer and an inner, the former 

 about one-half the thickness of the latter, and separated from it by a stratum 

 of granules so minute as to more nearly resemble a membrane. The outer 

 surface of the cuticula is provided with a similar membrane, since there are no 

 cirri or pseudocilia whatsoever. A distinct, tho very thin basement mem- 

 brane, is also to be seen. The two strata of the cuticula seem to be of pretty 

 much the same consistency since they stain about the same, altho the outer 

 constantly appears somewhat darker at first sight on account of the proximity 

 of its two bounding membranes. On the scolex the outer layer is modified 

 into extremely short and fine spinelets, which, while absent from the terminal 

 disc as well as the posterior borders of the segments, are well developed in the 

 bothria and out over the edges of its walls. 



The subcuticula has the usual reticular appearance, is about 58/i in thick- 

 ness and is provided with numerous comparatively large nuclei (5 to 7.5^* in 

 diameter) distributed equally thruout the tissue, excepting for a stratum about 

 15ju in thickness immediately beneath the cuticula, which is almost constantly 

 free of them. This outer layer is, of course, composed of the processes of the 



