3 
H. A. Baylis 
according to the state of contraction. It is, in any case, considerably wider 
than the “neck” which follows it. Its diameter, measured from side to side, 
is from 0-21 to 0*26 mm., with a mean measurement of about 0-24 mm. The 
suckers, situated somewhat laterally, have an outside diameter of 0*075 
0*093 mm. There is a well-developed rostellum, having a diameter of 0*07- 
0*08 mm., and armed with a single row of hooks of the characteristic shape, 
21 or 22 in number (rpost commonly 22), and 19-20 /x in length. 
The “neck” is unsegmented for some little distance behind the scolex. 
The total number of recognisable segments in the strobila may reach 000 oi 
more. Rudiments of genital organs begin to be recognisable at about the 
50th segment from the anterior end; “mature” segments i segments 
Fi'T. 2. Hymenolepis longior. Scolex, with evaginated rostellum, viewed ev face. 
containing male and female organs in a state of full functional activity—at 
about the 250th. The number of gravid segments at the posterior end varies 
between (roughly) 00 and 100. The segments are broader than long through¬ 
out, though the length tends to become nearly equal to the breadth in the more 
posterior segments, and the ratio of length to breadth is (except in greatly 
contracted specimens) much higher in mature segments than in corresponding 
segments of //. nana or H. nana fraterna. 
In a mature segment (Fig. 3) the most conspicuous organ is the ovary, 
which is large and compact, rather irregularly but not very deeply lobed, and 
occupies roughly one-third of the width of the segment, having a greatest 
diameter (from side to side) of about 0*15 to 0*17 mm. The ovarian ova have 
a diameter of 0*015 mm. The yolk-gland and shell-gland lie in the usual 
1—2 
