84 Transactions of the Royal Canadian Institute [vol. x. 



for material cleared in oil of cedar, which is very brittle, to break immed- 

 iately behind the ovary is the only other indication, apart from the re- 

 productive organs, of proglottidation. This tendency, however, so far 

 as could be determined is not based on any differentiation of the paren- 

 chymatous tissues internally at this level but more probably on mere 

 differences of support in the latter, the ovary rendering the parts immed- 

 iately ahead more resistant to strain. The following are some relative 

 measurements of a typical strobila (Fig. 3) : — 



Proglottis. Length. Greatest Width. 



20 1.85 mm. 0.48 mm. 



22 2.37 mm. 0.48 mm. 



24 2.03 mm. 0.58 mm. 



What is apparently the end-proglottis is rounded posteriorly (Fig. 12) 

 and provided with a functioning set of genital organs. The endings of 

 the excretory vessels in this joint, however, seem to point to some part 

 of the strobila (perhaps, also, of the plerocercoid) being lost at an early 

 stage (vide infra) . 



Cuticula. 

 The cuticle, a well-developed structure excepting in the oldest portions 

 of the strobila where it is often much torn or even missing over small 

 areas, is from 3 to 4)li in thickness. It is divisible into two principal 

 layers in each of which other layers can be distinguished. The outer of 

 these, about two-thirds as thick as the inner, does not stain as well as the 

 latter owing to the fact that it is made up of alternating dark and lighter 

 areas arranged so as to give a striated appearance. The darker lines 

 seem to be composed of minute granules while the lighter are more 

 homogeneous (Fig. 7). Bounding this layer peripherally there is to be 

 seen in many sections an extremely narrow clear line, followed by a sort 

 of external limiting membrane, while in others, especially those through 

 young strobilas, only very minute teeth which seem to be continuations 

 of the darker lines are visible. The inner layer of the cuticula takes 

 stains much more readily than the outer and is quite homogeneous with 

 the highest magnifications. The line separating the two, however, is 

 slightly darker than even the inner, which is perhaps due either to larger 

 granules than those in the dark lines of the outer layer or a greater num- 

 ber packed more closely together. Bounding the inner layer on the 

 inside there is a well-developed basement-membrane, brought out best 

 by Mallory's stain. This is often separated from the homogeneous 

 layer by a clear line as indicated in the figure. Then again just outside 

 the basement-membrane the former is slightly granular in some quite 

 thin sections. The cuticle is traversed at short intervals by the minute 



