694 Variations in a Copepod Crustacean. [September, 
its inner margin, the three first of which gradu- 
ally become larger from base upwards, and bear 
each, one invaginate spine, the fourth is slightly 
produced inferiorly (the rounded tip being finely 
ciliate down to the produced lower middle), 
there (at the lower middle) bearing two spines 
directed downward, and a very fine long flagellum 
at its tip. The arrangement of the bristles of 
the last two joints, as well as the general outline 
of the whole, differ from Diaptomus sanguin- 
cus F, 
The inner branch of the first of the four pairs 
of natatory legs has two, the rest three joints 
(see Fig. 8). Their purpose is aération of the 
blood as well as locomotion. 
The fifth pair of legs in the female is bi- 
Fic. 7.—Inferior TAMOse, both branches arise from a two-jointed 
or second maxilli- basal piece (coxa and trochanter), the inner 
ts branch is short, straight, slender, not jointed, 
abruptly terminating in a conical tip surrounded with micro- 
scopically small spines around a longer median one; at the side 
of the tip and opposing each 
other are two longer, mova- 
ble (?) spines. The outer branch 
arises from the second broad 
basal joint, and is strong, two- 
jointed, terminating in a sin- 
gle, interiorly (near the tip) fine 
serrate claw, which has exte- 
riorly two (one longer and ong 
shorter) diverging spines a lit- 
tle above its middle (Fig. 9): 
The office performed by the 
transformed fifth pair of legs 1m 
Fic. 8.—Form of second, third and female individuals is not suffi- 
fourth natatory legs. xx, inner branch; ciently known. They may be 
x, outer branch. - 
for the protection of the eg¢ 
sac or for properly placing the same, or perhaps they cooperate 
with the male in copulation. In some cases they may burst oF 
pierce the spermatophores fastened below the female genital pore. 
