93 
incubation was found to extend over several weeks at 
least. In one case the ovisaes were kept for six weeks, 
and in another eight weeks, before the embryos hatched. 
The incubation takes longer than that, however. In 
both cases the embryos were pigmented when placed 
under observation. The first appendages that make their 
appearance are the antennules, antenne and mandibles. 
They are in a rudimentary state, and the embryo is now 
ready to hateh. During this period the embryo increases 
in size as it develops. 
The whole of the embryos contained in the tube hatch 
practically at once. The enclosing membrane ruptures, 
then the membrane of the tube splits, and the nauplii 
after freeing themselves from the fragments swim to the 
surface. Plate I., fig. 5, represents a newly hatched 
nauplius, the natural size of which is "46 mm. It leads 
a pelagic life for a time, and grows by successive moult- 
ings. It next settles down on some fish, and passes into 
a evelopoid state (Plate I., fig. 5). The young parasite 
immediately develops a thin chitinous filament from the 
median frontal gland already described, which passes into 
the tissues of the host, and it becomes fixed. The median 
sucker (b., Plate I., fig. 5), with the help of the rudi- 
mentary antenne and second mavxillipedes, enables the 
animal to bring its mouth into contact with the host. 
If young plaice, flounder, cod, &e., one to three inches 
in length, be examined very carefully at the end of the 
summer, it is practically certain that some recently 
attached Lepeophtheirus or Caligus will be found either 
on the fins or some other part of the integument. On 
examining fins which have parasites attached, the filament 
is seen passing through the skin, under it, and along one 
of the fin ravs, as shown on Plate I., fig. 5 (natural size 
mm.). The filament may have the end bluntly 
yy 
Lye 
