6 
Hymenolepis longior n. sp. 
Many authors have given measurements of Hymenolejris nana and “ H. 
murina ,” and it appears to the writer that, among the individuals ascribed 
to the latter form, some in reality belonging to the species now described as 
new have frequently been included. The new species appears, in fact, to have 
been confused with “//. murina ” ever since the original description of the 
latter by Dujardin (1845), and to have been responsible for some of the 
alleged differences between it and the H. nana of man. The discrepancies 
in the measurements of total length given by different writers for “ H. murina ” 
are greater than could readily be accounted for by different states of contraction 
in complete individuals of the same species. 25 mm. is given by several 
authors as the maximum for H. nana, whereas “ H. murina ” is frequently 
said to reach 40 or 45 mm.—the latter figure agreeing with that given above 
for H. longior. According to Mr Dudgeon’s material, H. nana fraterna (the 
true “H. murina ”) rarely exceeds 20 mm. in length, unless abnormally 
stretched. Other measurements, such as those of the maximum width of the 
strobila, the width of the scolex, and the diameter of the suckers, are so variable 
that little reliance can be placed upon them. They are certainly, as Joyeux 
(1919) has pointed out, useless as criteria for distinguishing H. nana from 
H. nana fraterna; and they seem to afford as little help in separating H. nana 
fraterna from H. longior. It may be mentioned that some of the extreme 
measurements given by previous writers, especially for the width of the 
strobila and the diameter of the suckers, find no parallel among the present 
material. Thus the width of H. nana has been recorded as reaching 0-7 mm., 
and that of “ H. murina ” 0-9 mm. Similarly the diameter of the suckers in 
H. nana is said to be sometimes as much as 0-105 mm. Reference to the table 
given above will show that nothing approaching these figures has been ob¬ 
served among Mr Dudgeon’s material, and it may be suspected that some of 
them, at least, are erroneous, or due to excessive artificial pressure on the 
specimens. Much, of course, depends upon technique in handling soft-bodied 
worms, and for this reason the value of such measurements is often questionable. 
In the present case there is one character, depending only in part on 
measurements, which seems to be of great importance. The inner shell of 
the egg, being composed of a relatively hard, chitinoid substance, is not 
subject to alteration by pressure or the action of reagents to the same extent 
as the soft parts. It has been repeatedly insisted upon that the inner shell 
of the egg of “ H. murina ” is lemon-shaped, and provided at each pole with 
a well-developed knob-like thickening; whereas in the egg of H. nana the 
inner shell is more rounded, with the polar knobs scarcely distinguishable, 
but with a filamentous process at each pole. Unfortunately the measurements 
of the inner shell have seldom been given. Von Linstow (1896) gives the 
following: 
nana: 0-028 mm. (exceptionally 0-029 x 0-024 mm.), usually spherical. 
murina: 0-031 x 0-023 mm., lemon-shaped, with knobs at the poles. 
The lemon-shaped inner shell, with polar knobs, is highly characteristic 
