III BRANCHIURA—ARGULIDAE 77 
position. They are ectoparasites upon various species of fish, 
Argulus foliaceus being common in the fresh waters of Europe, 
infesting the branchial chamber or the skin of fresh-water fish, 
but being frequently taken swimming freely in the water. 
map| 
Fic. 48.—Argulus foliaceus, young 6, x 15. a, a*, First and second antennae ; ab, 
abdomen, /, compound eye ; Z, liver ; m, mandibles and first maxillae ; ma, second 
maxilla (the median eye is seen between the two second maxillae) ; map, maxilli- 
pede ; s.g, shell-gland; sp, spine; ¢, testis; 1, 4, first and fourth swimming 
appendages. (After Claus.) 
Both males and females can swim with great agility, and they 
leave their hosts regularly at the breeding season in spring and 
autumn; fertilisation is internal, and the female deposits the 
eges on stones and other objects. After leaving its host, an 
Argulus, if it cannot find a fish of the same species, can live 
on almost any other species, and may even attack Frog tadpoles ; 
while the kinds that infest migratory fish can change with their 
