2 
Hymenolepis longior n. sp. 
H. nana fraterna. A recent important contribution to the question is that of 
Joyeux (1919). This author returns to the position taken up by v. Linstow, 
in regarding the forms as distinct species. He proposes to call the rat-parasite 
H. fraterna. 
The supposed morphological differences between H. nana and “ H. murina ” 
must be discussed more fully later. It will be well, however, first to consider 
Mr Dudgeon’s Hymenolepis material, which appears to have rather important 
bearings on this question. 
Among the material there occur three forms, viz. 
(1) Hymenolepis diminuta (Rud.). 
(2) A form which may be called H. nana fraterna. 
(3) A form very closely related to the latter, but quite distinct, which 
does not appear to be referable to any of the other species of Hymenolepis 
Fig. 1. Hymenolepis longior. Two scolices in dorsal or ventral view: A., with 
evaginated rostellum; B., with invaginated rostellum. 
from rats or their relatives, of which the descriptions are accessible to the 
writer (see list, p. 7). This form, accordingly, it is proposed to regard as a 
new species. 
Hymenolepis longior , sp. n. 
The worm is very slender, fragile and semi-transparent. Complete speci¬ 
mens attain a length of 45 mm., or even 60 mm. in a stretched condition. 
The maximum width of the strobila (usually occurring in the region of the 
gravid segments, but sometimes, in contracted specimens, more anteriorly), 
is from 0*42 to 0-53 mm. In exceptionally contracted individuals it may even 
reach 0*65 mm. The scolex is flattened dorso-ventrally, more or less rect¬ 
angular in transverse section, and assumes very different shapes (Fig. 1) 
