Marshall and Severin—Anatomy of Ranantra fusca . 499 
seminal vesicle differs from the anterior section both in thickness 
and in its cellular structure. In sections (PL XXXVI, Fig. 21) 
it is seen that two muscular layers are present, an outer longitu¬ 
dinal, and an inner circular one. There is a single layer of epi¬ 
thelial cells, each with a small spherical nucleus near its base and 
cell boundaries which were discernible only for about one-third 
the distance from the basal membrane to the free end of the cell. 
Here the boundaries disappeared, some at a greater distance from 
the base than others,, so that no limit to the cells could be dis¬ 
tinguished. There was- apparently quite a difference in the 
structure of the cell at different parts, the distal half showing a 
number of large vacuoles which are not present near the base, 
and also showing very distinctly a longitudinal striation. The 
lumen of the tube was very small or often not discernible. 
Where the lumen had disappeared, its position was filled with a 
mass which was seemingly a, continuation of the cells and dif¬ 
fered from them only in the direction of the striation. When 
a longitudinal section of part of the tube is seen, the striations 
nearest the base are at right angles to the wall of the tube, but. 
towards the center they all turn in one direction as if there was a 
flowing out from the tube. The cells have a glandular appear¬ 
ance and it would seem that the secretion; formed was filling or 
had filled the lumen of the tube 1 and was being carried slowly to 
the outside. 
This last part of the vas deferens is short, and, uniting with 
the one from the other testis, forms- a short, median tube, the 
ejaculatory duct, which passes into the base of the penis. The 
structure is here different from any other part, of the tube. The 
epithelial cells are small and nucleated and between them we 
were unable to distinguish any boundaries. The free ends of 
the cells were lined with a wrinkled layer of chitin, while at 
their base was a thick layer of circular muscles. These entirely 
surrounded the epithelial layer and made up most of the thick¬ 
ness of the wall. 
Reproductive organs ; female .—-(PL XXXVI, Figs. 23, 24.) 
Each ovary consists o-f five ovarian tubules each with a terminal 
nutritive chamber followed by a number of egg chambers. The 
five nutritive chambers are situated within the first abdominal 
segment; they are held together by tracheal tubes and connective 
tissue, making it very easy to remove the tubules of each ovary as 
one piece. In all our specimens, collected in autumn, the tubules 
