Lepeopbtbeirus dissimulatus — -Lewis 
241 
two exceptions were chalimus larvae found at- 
tached to the gill membrane of Acant kurus tri- 
ostegus sandvicensis . The number of larvae pres- 
ent in the buccal cavity of infected fishes ranged 
from 1 to 203. In the specimen of Acanthums 
olivdcem possessing 203 attached copepodites 
and chalimus larvae, the roof of the mouth ap- 
peared to be actually shingled with copepods. 
After breaking free from the attachment fila- 
ment, the fifth or sixth chalimus moves out of 
the buccal cavity either into the gill cavity or 
onto the external surface. The final moult, from 
the sixth chalimus to the adult, is accomplished 
outside of the buccal cavity. Only one observa- 
tion of the final moult was made and this was 
after the adult had broken through a split in 
the anterior dorsal surface of the sixth chalimus 
cuticle. At the beginning of the observation the 
animal had pulled the second antennae free 
from the old cuticle and was not actively mov- 
ing, holding on to the host by means of the 
maxillipeds and keeping the second antennae 
free. After a short period of time the second an- 
tennae were used to grasp the surface and the 
maxillipeds and remaining appendages were 
pulled free from the cuticle. By means of violent 
wriggling of the body and appendages, the cu- 
ticle was shed over the posterior end of the 
body. After a second short period of time, dur- 
ing which the newly emerged adult remained 
attached by. the second antennae, all of the tho- 
racic appendages and the maxillae were moved 
randomly and the animal then assumed the adult 
role of skittering over the surface of the host. 
Fertilization occurs just after the terminal 
moult. The male at this stage of development 
is almost completely grown; the female is still 
small and will increase in size in the adult stage. 
The actual placement of the spermatophores, 
held within the genital segment of the male, was 
not observed. Several mating pairs were col- 
lected and observed, however. The male was 
found to clasp the fourth pedigerous segment 
or the anterior end of the genital segment of 
the female with the second antennae. The func- 
tion of the maxillipeds in mating was not de- 
termined, although in all observed pairs the 
maxillipeds of the male were free. A. Scott 
(1901:28) and Wilson (1905:528) indicate 
that the caligid spermatophore is viscid and, 
as noted for L. dissimulatus , that it forms an 
oval or tear-shaped body in the posterior region 
of the genital segment. The male presumably 
bends the posterior region of its body, the free 
segments, underneath itself and, upon contact 
with the posterior ventral surface of the female, 
discharges the two spermatophores which ad- 
here to the genital segment of the female. No 
remating was observed and, as suggested by 
Wilson (1905:527), the single mating just after 
both sexes moult into the adult probably suffices 
for the entire egg production of the female. 
The young adult female was found in both 
the gill cavities and on the external surface of 
the body. Large females carrying egg strings 
were found primarily in the gill cavity. The co- 
pepod appears to have more protection in the 
gill cavity, especially against being swept off 
of the host by water currents or brushed off 
when the host comes in contact with the sub- 
strate. The position of the female on the host 
thus may be dependant upon its size and upon 
the presence or absence of egg strings which, it 
appears, add a considerable burden. 
The duration of the adult life is not known. 
Females kept in the laboratory produced up to 
three sets of egg strings, each string being ex- 
truded approximately 21 hr after the previous 
string had hatched. Thirty to 40 hr is the av- 
erage interval between extrusion of the eggs 
and hatching. The period of time between fer- 
tilization and the production of the first pair 
of egg strings is not known, neither is the time 
from moulting into the adult until the female 
is fertilized. Further, the conditions provided in 
the laboratory were far from those in the natural 
environment and it is felt that the number of 
egg string sets produced is probably more than 
the three obtained in the laboratory. 
SUMMARY 
1. The external anatomy of the 10 stages in 
the life history of Lepeophtheirus dissimulatus 
is described and figured. 
2. The general behavior of the various stages 
is discussed. The first two, the nauphar stages, 
are planktonic. The third or copepodite stage is 
planktonic early in its existence but later at- 
taches to the fish host by means of the prehen- 
sile second antennae. After attachment, the co- 
pepodite secretes a frontal filament that is em- 
