34 
Journal of Agricultural Research 
Vol. I, No. i 
average 78/*. The average length of 36 small hooks of T, ovis (adult 
and larva) having a range of 96 to 128// was 113/*, with the blade 
ranging from 48 to 60 fi, average 57/1. In form the hooks of T. hydatigena 
and T. ovis are very similar. The small hooks may be distinguished 
from each other by the fact that the ventral root, though transversely 
enlarged in both species, is rather deeply bifid in T. hydatigena (fig. 6, r), 
a condition which is absent in T . ovis or at most only faintly indicated. 
Of the more common tapeworms of the dog the one with which Taenia 
ovis seems most likely to be confused is T. hydatigena (T. marginata), the 
adult of Cysticercus tenuicollis . Apart from the differences exhibited by 
the hooks as noted above, the segments of the strobila show certain 
characters by which the two species may be differentiated. (PI. II, 
figs. 3, 4, 5; and text fig. 6.) The strobila of T. hydatigena is thicker 
(dorso-ventrally) relatively to its other dimensions than that of T. ovis 
and the latter has a tendency to twist spirally. The segments of T, 
hydatigena have a rather regular quadrilateral form, and the edge of the 
strobila is comparatively straight, whereas in T. ovis the segments have 
convex lateral borders, the convexity usually being well marked, and 
the edge of the strobila presents a scalloped outline. The posterior 
margin of the segment projects more prominently in the former than in 
the latter species. In T . ovis the genital pore is in a large prominent 
genital papilla, and there is a large and deep genital sinus; in T. hydatigena 
the genital papilla is small and the genital sinus shallow and inconspicuous. 
The testicles in T. ovis do not extend posterior of a line drawn through 
the anterior border of the yolk gland parallel with the posterior border 
of the segment; in T, hydatigena they extend beyond the posterior limits 
of the ovary and yolk gland practically to the posterior border of the 
segment (figs. 7 and 8). With respect to the branching of the uterus, 
T. ovis and T. hydatigena are quite different, the uterus of the former 
having 20 to 25 lateral branches from each side of the median stem, 
whereas the uterus of the latter has but 5 to 8 such branches (figs. 9 and 10). 
' Other well-known tapeworms of the dog, such as Taenia pisiformis 
(T. serrata) y Multiceps multiceps ( T . coenurus), Multiceps serialis (T, 
serialis ), Echinococcus granulosus (T. echinococcus ), and Dipylidium 
caninum , are less likely than T. hydatigena to be confused with T. ovis . 
In addition to distinct morphological differences, the small size of E. 
granulosus and D, caninum precludes any chance of mistaking them for 
T. ovis, T, pisiformis may be distinguished by the large size of its hooks 
(the large hooks being 225/4 or more in length) and the small number 
of lateral branches of the uterus (8 to 10). M, serialis may be dis¬ 
tinguished from T. ovis by the fact that the hooks are considerably 
smaller, the recorded limits of length of the large hooks being 135/4 and 
157/4, that the ventral roots of the small hooks are distinctly bifid, and that 
the genital papillae are small and inconspicuous. M. multiceps has large 
hooks about the same in length as those of T. ovis but with blades longer 
