18 
0.15 mm. to 0.17 mm. long, from 0.8 to 0.9 mm. broad; all the segments having 
their posterior angles somewhat salient, sharp, shaped like saw teeth; genital 
orifices unilateral; testicle [misinterpretation of seminal receptacle] claAdform, ex- 
tending transA'ersely from the middle to the receptacle of the penis in the shape of 
a retort: penis smooth, very slender, not A*ery sahent; eggs elhptical with three 
em’elopes; the external one 0.065 mm. long; the middle one membranous, in folds, 
0.05 mm. long; the internal one more resistant, somewhat oblong and terminating in 
an obtuse point at each extremity; embryo from 0.029 mm . to 0.030 mm. long, with 
hooks from 0.015 mm. to 0.016 mm. long. 
I found it at Eennes in a brown rat {Mus decumanus,) , in a dwarf field mouse {Mus 
pumilus) [=J/. minutas'], and in a garden dormouse {}fyo.vus nitela) [=EUomys 
querci ?/.s-] . ( Translation. ) 
Blanchard (1891a). Moniez (1888). and Linstow (1896a) inclined to 
the opinion that the two forms T^nia nana and Tcenia murina are 
distinct species. Blanchard (1896b). however, has more recently come 
to the conclusion that the sliglit inconstant diherences which have been 
noted in the two forms are sufficiently accounted for by the difference 
in habitat, and that the two worms should be united under one species, 
which he would for reasons of priority call Hymenolepls murina. But 
since the name Tcenia rnirrina used by Dujardin, is preoccupied, hav- 
ing been applied before 1815 to another form, it can not be retained in 
this connection. Tcenia nana Siebold. 1852 being the next available 
name, the correct designation of the species, placed in its proper 
genus, is therefore HyinenoJejyis nana. 
Linstow (1896a) believed he found differences which would justify a 
specific distinction between the forms in man and in the rat, but, as 
Massari (1898) has pointed out. his results are not entirely free from 
criticism, and his aro-uments rather unconvinciDg. 
Tlyrnenolepis nana may. accordingly, be regarded as occurring not' 
onh' in man. but also in the rat. and in the two hosts showing slight 
and Available differences, brought about by the action upon the para- 
site of an environment somewhat dilferent in the two cases. 
AXATOMICAL DESCRIPTIOX. 
EXTERNAL ANATOMY. 
As is well indicated by its name {nana. a dwarf] the worm under 
consideration is characterized preeminently by its small size (fig. 
5A). Being also very delicate, and likely to be broken in pieces, it 
is thus a difficult matter to discover specimens in the feces, unless 
passed in large numbers. 
Strobila. — Complete strobila? with gravid segments may be found 
ranging in length from 5 or 6 mm. (Blanchard, 1891a) to a maximum, 
as recorded so far. in man of 35 mm. (Mertens, 1892). In the rat a 
length as great as 45 mm. has been observed (Stossich. 1898). 
Favarcq (1891a) found a worm 75 mm. long, in the intestine of the 
garden dormouse {EJioniys yuercmus). which he believed to be a 
