42 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
dots being evidently the deeply stained nuclei of the small 
spermatic cells (see Pl. I. figs. 8 and 5). 
After about 20 sections from the posterior end the 
lateral lobes of testis are found to be encroaching upon 
the ovary in its centre so as to divide off a smaller dorsal 
lobe from the ventrally placed main mass (PI. I. fig. 2). 
In this region is found the apparently single genital duct. 
The dorsal ectoderm bends down in section 24 to form 
a slender epithelial tube which seems to join the wall 
of the ovary (Pl. IV. fig. 9, o.d.). The testis lobes come 
in contact dorsally at this point and may possibly join 
(Pl. I. fig. 3), so the tube might be vas deferens, or act both 
as oviduct and vas deferens. The dorsal lobe then dies 
out after a few sections, and the ovary is then represented 
by a nearly flat ventral plate which can be traced forwards 
to about the 90th section (counting from the posterior end). 
Figure 3 on Plate I. shows the typical arrangement in a 
number of sections, say numbers 25 to 45, where the 
ventral ovary and the two lateral testis lobes enclose a 
small triangular area, which will be occupied a little 
further forward by the alimentary canal. The whole is 
still surrounded by a delicate ectoderm with no trace of 
a distinct test. 
The next figure (Pl. I. fig 6) shows, in the 48th section, 
the most posteriorly placed part of the alimentary canal. 
It is a short dorsal diverticulum from the point where the 
cesophagus joins the stomach, and can be traced forwards 
through the sections into the cesophagus and then the 
pharynx or branchial sac. In about the 50th section we 
come upon the first trace of the test in the form of a thin 
layer of cuticle dorsally placed and co-terminous with an 
area of rather larger ectoderm cells. As one traces the 
sections forwards these ectoderm cells get larger, and the 
layer of test over them becomes thicker (see PI. I. figs. 7 
