20 
Mertens (1892) found the average length of a number of specimens 
to be over 20 mm., and the maximum breadth from O.T to 0.9 mm. 
The number of segments varied from 180 to 200, and this character 
was more or less constant, even with a variation of 3 to d mm. in the 
length. 
Miura & Yamazaki (1897) give a length of 20 mm., and a maximum 
breadth of 0.d8 to 0.86 mm., measured in the fresh state, 0.3 to 0.56 
mm. after preservation. 
Dujardin (18d5a) gives a length 
of 25 mm. , and a maximum 
breadth of 0.55 to 0.9 mm., from 
specimens from rats; Grassi & 
Calandruccio (1887a), a length of 
33 to 40 mm. : according to Lin- 
stow (1896a), incomplete speci- 
mens measured 23 mm., with a 
maximum breadth of 0.82 mm. 
Head . — The head (figs. 1. 
6-15) is more or less globular, 
flattened dorso-ventrallv, and 
when viewed in front is some- 
what rectangular, with its suck- 
er'^ at the four rounded angles. 
Its size has been given by vari- 
ous observers from 215 to 480 p. 
in width and 360 to 450 p in 
length. It is often difficult, how- 
ever, to tell where the head ends 
Fig. 12.— Head of H. nana. Enlarged. (After neck begins, especiallv 
Krantz from Kiichenmeister & Ziirn, [?1881], pi. 5, . . 
fig. 2 .) in certain states ot contraction, 
Fig. 13.-Head of H. nana with protracted rostel- ^hat it is liot alwaVS pOSSible 
lum. Enlarged. (After Krantz from Kiichen- . , i i 
meister & ziirn, [ 71881 ], pi. 5, fig. 3 .) to determine the length with any 
Fig. 14.— Head of T^nia murina Dujardin (=if. degree of aCCUraCV. Examples . 
7iana^. Enlarged. Original type figure. (After ® i " . 
Dujardin, 1845a, pi. 12, fig. A3.) ti'oiii the rat give measurements 
Fig. 15.— Head of T. murina Duj. {=H. naim) Avitli falling within the Huiits lioted 
protracted rostellum. Enlarged. Original type , i 
figure. (After Dujardin, 1845a, pi. 12, fig. A2.) above. In SpeClllienS both trOUl 
man and from the rat, measured 
in this laboratory, the head has ranged in width from 130 to 250 p. 
Suckei^s . — The suckers, globular in shape, measure from 90 to 150 p 
(Mertens, 1892). In specimens from the rat the}" seem to be generally 
smaller — according to Dujardin (1845a) 80 p, and after Linstow (1896a), 
79 /4, in diameter, while we have seen them here, in sizes from 70 to 
90 /4, measured after preservation. In the live worm the\" are very 
protractile, and may be extruded to a considerable distance (Grassi & 
Calandruccio, 1887a). When thus extruded they may be torn away and 
