NEW AVIAN CESTODE. 409 
wide. They increase rapidly in both dimensions on_ passing 
backwards, but are always broader than their length. 
Internal Anatomy. 
Musculature.—The longitudinal bundles of muscle-fibres are 
arranged in two layers, which are most strongly developed dorsally 
and ventrally, The outer layer consists of slightly smaller bundles 
than the inner layer, and is scantily developed towards the middle 
line of the segments, being more in evidence towards the sides. 
But neither layer is strongly developed quite up to the lateral 
margins. 
The inner layer consists of about 25 to 30 bundles. 
Transverse and dorso-ventral fibres are only feebly developed. 
Text-figure 2. 
Eel 
a, 
Tetrabothrius strangulatus. 
Semi-diagrammatic view of the anatomy of a young, sexually mature, segment, 
as seen from above by transparency. 
Ov., Ovary; R.S., the coil destined to become the receptaculum seminis ; 
Te., testes; Ut., uterus; Vag., vagina; Vit., vitelline gland; V.D., vas deferens. 
Nervous System.—The usual pair of longitudinal lateral nerves 
is present ; they are situated slightly beyond the most lateral of 
the inner longitudinal muscles. 
Exeretory System.—As usual, two pairs of wide longitudinal 
lateral vessels are present. The dorsal pair is situated almost 
exactly vertically above the ventral pair, and are of nearly 
the same diameter. The ventral canals are connected in the 
posterior part of the segments by transverse vessels. 
