392 
Tapeworms of Birds 
measured 4-048 mm. long by 0-807 mm. broad. The head is very like 
that of D. proglottina. It is provided with a slightly muscular spheralic 
rostellum 0-041 mm. in diameter, its an¬ 
terior extremity capable of invagination 
upon itself: it is situated at the bottom 
of a shallow apical depression of the 
scolex and lies anterior to the suckers. 
Usually it is extended, protruding half¬ 
way from the apex of the scolex. It is 
armed with 50-60 hooks (PL XIX, fig. 5) 
of the characteristic Davainea type ar¬ 
ranged in two rows. The hooks of each 
row alternate with one another, the 
distance between the transverse level of 
the head of a hook of one row and that 
of a hook of the other being so slight as 
to cause the hooks to appear in a single 
row. The hooks differ in size, those of 
one row being 0-0071 mm. long, those of 
the other 0-0084. This rostellum differs 
from that described by Blanchard (i) for 
D. proglottina in that it is spherical 
instead of hemispherical (although this 
may only be due to muscular causes), 
the hooks number 60 at the most instead 
of 95, and the “ large fosse circulaire entre 
le rostre et V infundibulum ” does not 
exist in this case. The four suckers are very shallow and are armed 
with approximately 4-6 concentric rows of hooks whose lengths vary 
from 0-0052 mm. to 0-0086 mm.: there is a tendency for the number of 
hooks to be less upon the posterior border than upon the anterior. A short 
neck is present. The strobila (PI. XIX, fig. 1) is usually composed 
of seven proglottides, but as many as nine may be present. The first 
two are broader than long, the next three quadrangular, and the suc¬ 
ceeding ones longer than broad: the terminal proglottis may be as much 
as 2^-3 times longer than broad. There is no sign of a division between 
the proglottides as figured for D. proglottina, nor of the peculiar concavity 
of the angles. (Compare Text-figure 1 with PI. XIX, fig. 1.) 
Attachment of Scolex. The scolex is only attached to the free surface 
of the duodenal mucosa (PI. XXI, fig. 23); it sometimes nearly reaches 
Fig. 1. 
Davainea 'proglottina (after 
Blanchard), x 95. 
