S. Yokogawa 
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bursal lobes are fully developed and entirely separated (Fig. 21, Plate X). The 
rays of both lateral lobes now consist of several cells and each ray has assumed 
its characteristic shape. The central dorsal ray usually consists of two cells, 
while the externo-dorsal rays are each made up of the projection from only 
one cell. 
The development of the spicules and the gubernacula. The spicules and the 
gubernacula have the same origin. They are produced by the long conical or 
spindle-shaped cells situated just back of the base of the rectum (Figs. 11-15, 
cs and s, Plate IX). In the beginning of the second parasitic stage these cells 
increase in size, while toward the end of this stage they decrease in number 
and produce the chitinous material of the spicules and the gubernacula. The 
spicules are produced at the sides of these cells and become extended very 
rapidly forward along the dorsal side of the intestine. They later reach a 
muscle cell-group which is present dorsally at a distance from the posterior 
end of the body. These muscle cells develop into the retractor muscles of the 
spicules, and come from one original cell (Fig. 19 ,rms, Plate X). This original cell 
at the beginning of the second parasitic stage is spindle-shaped and is located 
at the dorsal side of the intestine at a distance of about 0-22 to 0-23 mm. from 
the posterior end of the body (Fig. 13, rms, Plate IX). It is connected with the 
cells at the base of the rectum and with the subcuticular layer by tiny fibres. 
This spindle cell divides as the development of the sex-organs proceeds, forming 
two groups of muscle cells (Fig. 19, rms). These are the retractor muscles and 
extend anteriorly along the dorsal wall of the intestine with the further 
development of the sex-organs. Toward the end of the second parasitic stage, 
they are found at a distance of about 0-53 to 0*56 mm. from the posterior end 
of the body and become attached to the spicules. The spicules when first 
produced are transparent and colourless, while in the adult stage they have a 
brownish golden colour. The anterior ends of the spicules are slightly thickened 
and are attached to the retractor muscles, while their posterior ends are united 
and project from the dorsal side into the cloaca, forming a small arc. 
The gubernacula are produced from the chitinous substance in the distal 
portion of the spicules toward the end of the second parasitic stage. 
( d) The Development of the Female Reproductive Organs. 
(1) The Internal Sex-Organs. 
General description. The term “internal sex-organs” of the female refers 
to those organs which develop from the genital primordium and includes the 
ovary, oviduct, seminal receptacle, uterus and the ovijector. 
At the beginning of sexual differentiation, the genital primordium of the 
female migrates from the middle of the body to its posterior end. During this 
time, it can be found in different individuals in every position between the 
middle of the body and the anal region. After reaching a position just in front 
of the anus (Fig. 23, gp, Plate XI) the genital primordium increases in length, 
