1905. ] Anatomy of the Tsetse-fly (Glossina palpalis). oat 
a common origin, cannot be stated with complete certainty, but it seems at 
least highly probable. The morphological significance of this fact is, perhaps, 
that the two common stems of the Malpighian tubules are not to be 
considered as arising right and left from the gut, but as dorsal and ventral in 
origin. I have not succeeded in finding the distal extremities of the two 
remaining tubules, but they appear to pass down towards the ventral side of 
the abdomen and to be entangled with the genital organs, the dissection of 
which they help to render difficult. 
3d. The Genital Organs lie in both sexes close to the ventral side of the 
body in the hinder segments of the abdomen. 
The male organs (fig. 5) consist of two pairs of tubes, greatly convoluted 
for a whole or a part of their course, which open all together into an unpaired 
tube, the ductus ejaculatorius, which in its turn passes to the external organs 
of generation and opens on the penis. 
Commencing with the paired portions of the male apparatus, it is observed 
that the two tubes on either side differ markedly from one another. One 
pair, placed most posteriorly, is tightly wound and has the coiled portion 
pigmented. The other pair, more anterior, forms a looser coil and is without any 
pigment. Iidentify the former as the testis, the latter as the vesicule seminales. 
Hach testis commences with a delicate white filament (¢. f), embedded in 
the fat-body and difficult to trace. I have not succeeded in finding where the 
free end of the filament is attached; in dissections it appears to be loose. 
_ The filament passes on into the tightly coiled pigmented tube, which forms a 
conspicuous, compact, brown body, the testis (7Z.). In one dissection I 
succeeded accidentally in uncoiling the testis by pulling inadvertently on the 
filament when trying to remove the fat-body. It was then seen that each testis 
is a whitish coiled tube enveloped in a pigmented brown coat, which crumbles 
easily into a brown powder. In specimens that have been long in alcohol 
also the pigmented coat often sticks to the surrounding fat-body and comes 
away from the testis. The proximal part of the testicular tube is dilated 
and forms the testis proper; the distal portion is of smaller calibre and 
more tightly coiled, forming an epididymis, from which the tube is continued 
as the vas deferens (V. d.). The latter is a white, straight, or but slightly 
sinuous tube. The brown pigment of the testis is continued a very short 
way down the vas deferens, and ends abruptly. 
Each vesicula seminalis (V. s.) is a white tube, commencing with a blind 
end. A short distance from the commencement the tube is slightly thickened 
for a short distance. There is nothing to bind the coils together, nor any 
pigment, as in the testis. Distally the tube straightens out to open into the 
unpaired duct of the generative system. 
