74 
and exopodites also two-jointed, but no trace of endopo- 
dites. The external angles of the joints are furnished 
with short spines. The fifth pair are rudimentary, are 
attached to the posterior end of the genital segment, and 
consist of a thin lamella, furnished with three sete along 
the posterior margin. Situated on the. middle line 
between the second maxillipedes is a strong chitinous 
plate with a bifid apex pointing posteriorly. This is 
known as the sternal fork, but its function is unknown.* 
The external openings are the mouth, the vulve, the 
openings of the oviducts and vasa deferentia and the anus. 
The mouth (Plate I1., fig. 1 and fig. 8) is situated on the 
ventral surface of the cephalo-thorax, and is placed at the 
apex of a short, movable, conical tube. This tube is com- 
posed of the upper and lower lips fused together. The 
vulvee (Plate IT., fig. 6) are situated on each side of the 
middle line near the posterior end of the genital segment, 
‘ 
and communicate with the “receptacula seminis.” They 
are difficult to see in the adult female, but have each 
frequently a spermatophore attached which indicates the 
position. The openings of the oviducts are in the same 
segment, but nearer the lateral margins and just under 
the fifth feet. The openings of the vasa deferentia (Plate 
IL., fig. 5) are situated on the postero-lateral margins of 
the genital segment of the male. The anus is situated in 
the middle line at the apex of the abdomen. In 
addition to these more important openings, there are also 
apertures of pore-canals and glands on the anterior 
surface of the basal joint of the protopodites of the second 
and third pairs of feet, and also on the dorsal surface of 
cephalo-thorax and abdomen. The opening in some cases 
* Mr. I. C. Thompson suggests that the sternal fork appears to him to 
be a support or crutch, serving to raise the body sufficiently from the host 
to enable either the swimming feet or the mouth organs to be used, but 
I have not seen it used in this manner. 
