70 
mus” stage, when the maxillipedes are rudimentary. Pro- 
bably in the adult, it acts as a first aid in securing the 
animal to its host. Passing backwards from this sucker, 
but distinctly over it, there is a transparent rod (c, fig. 1, 
Plate I.; fig. 3, Plate III.), lying inside a triangular 
blood space, which terminates in a gland (cg, fig. 3, Plate 
Ill.). The gland is probably the organ that secretes the 
substance for the filament in the ‘‘chalimus”’ stage and 
the rod the remains of the filament. The filament and 
duct are in actual contact during the early part of the 
parasite’s life (Plate I., figs 4 to 6, c). The eyes, two in 
number, are situated in the middle of the cephalo-thorax. 
The frontal and lateral margins are surrounded by a trans- 
parent membrane with faint transverse lines. This 
membrane is simply an extension of the chitinous exo- 
skeleton which covers the whole animal. It has 
frequently a serrated edge caused by tearing. 
The second part of the body is very small, and repre- 
sents the fourth thoracic segment of the pelagic Copepoda. 
The fourth feet are attached to the external margins of 
this segment. 
The third part of the body known as the “ genital 
segment,’ is of variable shape, according to the degree 
of maturity of the reproductive organs. In an immature 
female (Plate II., fig. 6), it is usually very little larger 
than the fourth part, whilst in a mature one it is nearly 
as large as the cephalo-thorax. The genital segment of a 
mature female is somewhat quadrangular in outline, 
shghtly wider posteriorly than in front. The same 
segment in a mature male (Plate I., fig. 2) is oval in shape 
and about one-third wider than the fourth part. 
The fourth part of the body is short and narrow, being 
only one-fourth of the width of the female genital seg- 
ment, and corresponds to the abdomen of the pelagic Cope- 
