22 
found seven with 24 to 26 hooks, one with 30; Blanchard (1891a) gives 
24 to 28 as the normal number. All of these observations were made 
upon specimens from man, while specimens from the rat, according to 
Dujardin (1845a) and Krabbe (1865) possess 20 to 24; Linstow (1896a) 
finds 23 to 24. The hooks possess a rather long, somewhat curved 
dorsal root, directed forward on the rostellum, and, directed backward, 
a thick, heavy ventral root which is about equal in length to the sharp 
pointed prong, forming with it a sort of fork. 
The roots of the hooks are more or less deeply embedded in the sur- 
face of the rostellum, and according to Mingazzini (1899) possess their 
own musculature, namely, fibers which are found in the inner sac of 
the rostellum. 
The size of the hooks has been given as 14 to 18 /^. Krabbe (1865) 
gives the size in worms from the rat and mouse as 10 to 13 yw, but no 
other observer has found them so small. Linstow (1896a) would draw 
a distinction between the hooks of the worms as found in man and in 
the rat, but comparisons made in this laboratory of forms from both 
hosts show them identical both in shape and size. 
Neck . — The neck (fig. 11) usualh" is slender, and somewhat less in 
diameter than the head, but this character varies with the state of con- 
traction. Its width may be defined by the limits 80 and 300 //, and 
its length to the first appearance of segmentation, 80 yw and 1 mm. or 
more. 
Segments . — As usual in tapeworms, segmentation is at first very indis- 
tinct. The segments are broader than long, and trapezoidal. The 
posterior border of each segment thus projects lateral!}^ beyond the, 
anterior border of the following* segment, making the edge of the stro- 
bila serrate. The }munger segments are 6 to 10 times broader than 
long, a ratio which decreases toward the posterior end. Occasionally 
some of the posterior segments are seen stretched out so that their 
length exceeds their breadth. The width of the strobila gradually 
increases toward the posterior end, at or near which it reaches the 
maximum size alreadv given. The last few segments mav graduallv 
decrease in width, and in a complete worm the last one is rounded off 
(figs.3,30)._ 
Genital g>ore . — The genital pores (figs. 22-24, 28, 31-33) are located 
toward the anterior border of the segments, one in each segment, and 
all upon the left side, except as occasionally one is found iq^on the 
right side. 
INTERNAL .\NATOMY. 
As in all cestodes, the spaces among the various organs are filled with 
a connective tissue known as Calcareous corpuscles.^ often 
large and present in great numbers amid the parench 3 *matous tissue of 
tapeworms, are comparative^ small and few in II. nana. 
