F. H. Stewart 
41 
Excretory system. Pore 0-238 mm. from the anterior extremity opposite 
the junction of the anterior and middle thirds of the oesophagus. The excretory 
duct is formed by the cells of the ventral line, and is lined by a fine membrane. 
The body of the excretory cell (Fig. 4) lies as usual beneath the oesophagus, 
joining the two lateral lines. The single large nucleus, 0-024 mm. long, lies in 
the left half of the cell. From the body two thin thread-like prolongations 
extend backward nearly to the level of the anus, intimately attached to the 
inner surfaces of the lateral lines (Fig. 3). Each prolongation contains a fine 
canal from its hind end to 0-5 mm. from its anterior extremity. It will thus 
be seen that these canals cannot be traced into the body of the cell or into 
connection with the excretory duct. The prolongations are the lateral 
canals. 
Gonads. Male—a single solid rod of cells ventral to the intestine, 2 mm. 
long, extending forward from the anus. Female—vulva patent, in the ventral 
line, 3 mm. from the tip of the tail. The vagina extends backwards and slightly 
to the left, and divides into two utero-ovarian tubes, one lying ventral to the 
intestine, the other along its left side. The former reaches to 2 mm., the latter 
to 2-3 mm. from the tip of the tail. 
c 
IV. The development of certain organs in A. Suilla Duj. from the 
EMBRYO AT HATCHING TO THE LARVA DESCRIBED IN SECTION III. 
Cuticle and lateral membranes (Figs. 5, 6 and 7). In the embryo the cuticle 
is excessively fine, lateral membranes absent. The lateral membranes appear 
on the 5th day, and are recognisable both in larvae from the liver and from 
the lung: they are extremely small. They become more prominent, and the 
skeleton appears, during the passage up the bronchi and trachea on the 8th, 
9th, and 10th days. The cuticle thickens markedly on the arrival of the larvae 
in the alimentary canal. The growth of the cuticle and lateral membranes 
appears to be continuous, and I have not observed any sign of an ecdysis 1 . 
Oesophagus. In the embryo it is represented by nuclei arranged as a narrow 
cylinder expanding at the hind end into a bulb. There is therefore no doubt 
as to the multicellular origin of the organ. 
Excretory cell. The nucleus can be identified (Fig. 8) in the embryo on 
the left side, opposite the anterior end of the bulb. In sections of larvae of the 
fourth day after hatching, the cell can be seen to belong to the left lateral 
line. By the fifth day it has grown underneath the oesophagus across the mid¬ 
line, and established contact with the right lateral line. The lateral canals are 
formed between the 14th and 19th days after hatching. The excretory system, 
with the exception of the terminal portion of the duct, is composed of one 
very large branching cell only. The wall of the terminal portion of the duct 
is formed by cells of the ventral line. 
1 This statement refers only to larvae after entry into the tissues of the host. An ecdysis 
occurs immediately after hatching, in the alimentary canal of the host. 
