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to the Gnathiidae, is parasitic upon the bodies of fish, the hosts 

 usually chosen by Paragnathia being the small flat-fish, which are 

 frequently so common in brackish waters. This larva, or as it 

 is generally termed, the praniza, unlike the adult, has the mouth- 

 organs present in the normal number and adapted for piercing and 

 sucking, forming a sharp oval cone, which the parasite plunges 

 into the body of its host, clinging to the skin of the latter by means 

 of the strong claws of its first pair of legs. It is nourished by the 

 juices of the fish to such an extent that the middle of its body 

 swells up to a large size and provides the animal with a con- 

 siderable reserve store of food. When full-grown the praniza 

 relinquishes its victim and makes its way to the shore, where it 

 casts its skin and assumes an adult form utterly different from the 

 one which it has just discarded. I came across large numbers in 

 the act of changing their form at the beginning of May in last 

 year: the pranizas were particularly striking on account of their 

 vivid coloration, most of them being of a brilliant yellow or 

 orange occasionally shading into brown, whereas the adults are 

 of a uniform grey or dirty white shade. In the adult stage this 

 crustacean is particularly terrestrial in habits, being found in small 

 cavities in the banks just below high-water mark, where a number 

 of specimens are usually found together, the males apparently 

 having small holes leading from these cavities into which they 

 retire in case of danger. They are very sluggish in their habits, 

 and when frightened frequently sham death, folding the legs along 

 the body. Strange to say, when they reach the adult state, these 

 animals appear to have solved the great problem of our existence, 

 how to live without eating, and it seems probable that, like the 

 members of the related genus Gnathia, they can live for several 

 years entirely without food, and without the trouble and exertion 

 of taking a single meal during the year. The female has no 

 internal organs whatever save a nerve-cord, the whole body-cavity 

 being occupied by the eggs or developing larvae, but, unlike 

 Clypeoniscus, its legs and other appendages, with the exception of 

 the mouth parts, are well-developed, and it leads a perfectly 

 independent existence. It is a strange looking object, as the 

 middle of its body is immensely distended and perfectly trans- 

 parent, while the head and tail are so small as to be hardly 

 noticeable, and one always expects it to collapse with a squeak 

 like one of these inflateable pigs which so delight small children. 

 The male is of a much more compact build, but is remarkable for 

 the size of its head and its fierce-looking, though apparently 

 almost useless, mandibles, the whole affair giving it a top-heavy 

 appearance. It has the mouth-parts of a very peculiar structure, 

 which it is almost impossible to describe accurately without the use 

 of illustrations : they are very widely separated in structure from 

 those found in the members of the genus Gnathia in which this 

 species was formerly placed, and I have, therefore, transferred 

 it to a new genus to which I have given the name Paragnathia. 

 It is very closely related to Euneognathia, a genus created by Mr. 



