LOBSTERS , CRAYFISH, ETC. 
271 
family, Sergestidce, in which the gills are impoverished or lost, while the first 
pair of trunk-legs and sometimes the second are simple, the chelaa of the third are 
minute, and the fourth and fifth pairs 
are feeble, rudimentary, or absent. To 
this family belongs the genus Leucifer, 
remarkable for having; the eves and 
antennae supported at the end of a long 
neck which extends in advance of the 
mouth. The gills are absent, respiration 
being effected by means of the general 
integument, which is so thin that the 
internal organs can be seen. In the 
figure the dark line (n) is the ventral 
nerve - chord which throws out finer 
branches from ganglionic swellings in 
each of the segments; ( h) is the heart, 
while immediately below the latter is 
the stomach, passing forwards into the 
gullet and backwards into the intestine. 
Cleft-Footed Group, —Order 
Schizopoda. 
This name is applied to a group 
nearly allied to the long-tailed Decapods; 
the chief difference between them being 
in the fact that in the present order the 
eight thoracic limbs are similar in struc¬ 
ture, each being pediform and provided 
with a distinct exopodite on the second 
segment. The gills, which are attached 
either to the thoracic or abdominal 
appendages, generally project into the 
water, and are but rarely concealed in a 
chamber. The eggs are carried by the 
female beneath the trunk, and are fre¬ 
quently protected by the development of 
a pouch. The order contains several 
families embracing a large number of 
mostly marine forms, some of which occur 
at great depths. Of the British species, 
the finest is Nyctiphanes norvegica, which 
forms an important part of the food of long-necked shrimp, Leucifer (much enlarged), 
herrings. It has luminous organs on the 
thorax and abdomen, and when swimming in a glass vessel, in a darkened room, 
appears like a flash of light. The young, as in all the members of the family 
