THE GNATHIIDZ 337 
When the young are ready to escape, the cuticle of the 
mother, previously separated from the hypodermis, splits 
into scales on the various segments. 
In the young the mouth-organs project beyond the 
head, and are evidently formed for piercing and for suction ; 
the mandibles have stiliform ends, and are followed by 
two pairs of slender organs, which are considered to be 
the two pairs of maxille; the maxillipeds are also slender 
and elongate; and the first gnathopods are elongate, 
limb-like, with the normal seven segments; the first 
perseon-segment is distinct, the fourth, fifth, and sixth 
being perhaps fused in the young female and distinct in 
the young male. Dr. Dohrn considers it inappropriate 
to speak of the mandibles as without ‘palp;’ rather, he 
says, it is only the ‘ palp’ which appears to be present. 
It is said to be easy to keep the males alive for a year 
or two in asmall bowl containing some of their native mud 
and some sea-water. As they are active climbers, pre- 
cautions must be taken against their escape. 
Gnathia, Leach, 1814, has long been the only genus 
contained in the family, to which it is entitled to give its 
name, as hinted by Bate and Westwood, and properly 
decided by the late Mr. Oscar Harger. For a long time 
the name Anceus, Risso, 1816, was used for the males, and 
Praniza, Latreille (Leach MS.), for the females and young. 
M. Eugéne Hesse has the credit of having definitely esta- 
blished the relationship between the two forms, but it 
should not be forgotten that Leach had expressed his con- 
viction of it as long ago as 1814. The female had already 
been figured and described as a marine Oniscus by Slabber 
in 1769. The best known British species is Gnathia maail- 
laris (Montagu) 1804. The ‘mandibles’ of the male dis- 
tinguish it from the species Gnathia Halidan (Bate and 
Westwood), instituted by those authors in 1866 with an 
expression of some doubt as to whether it might not be 
the same as Ginathia formica (Hesse). The American 
species, Gnathia cerina (Stimpson) may likewise be dis- 
tinguished by the ‘mandibles.’ M. Hesse has described 
seventeen species from the coast of France, and given draw- 
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