ARTHROPODA 285 
which they live. The eggs require for their developement a 
current of water, which is produced by the action of the 
abdominal swimming-feet of the parent. The group is ex- 
clusively marine; the members of it inhabit shallow water, 
and either live in crevices in coral rock, or burrow in the sand. 
They often rest in the mouths of their burrows with nothing 
but their eyes exposed above the sand; in this way they lie 
in wait for their prey, which they seize with astonishing 
rapidity by means of their powerful subchelate maxillipedes. 
They are extremely active in their movements, and difficult to 
catch, retiring to the inner end of their burrows at the slightest 
alarm. 
Sub-order 3. SCHIZOPODA. 
CHARACTERISTICS.—Small Thoracostraca ; the carapace is large 
and soft, the eight thoracic limbs are biramous. . Those modi- 
fied to form maxillipedes do not differ markedly from the 
others. The eyes are stalked. 
The Schizopoda retain throughout their life a condition 
which resembles that of the last of the series of larval forms 
which take part in the metamorphosis of some macrurous 
Decapods. This larva is known as the Mysis stage, and is 
called after the opossum-shrimp, one of the best-known 
Schizopods. 
The members of this sub-order differ markedly from the 
Stomatopoda, in which group the maxillipedes attain the greatest 
importance, for in the Schizopods each of the eight pairs of 
thoracic appendages are biramous legs, none of them being 
modified to form maxillipedes, although the two anterior pairs 
may tend in a shght degree to resemble the mouth appendages. 
The first antennae are biramous, and in the male are provided 
with a curious comb-like structure covered with olfactory hairs. 
The second antennae, a pair of mandibles, and two pairs of 
maxillae complete the appendages of the head. 
The carapace is large, and attached to the body only by a 
narrow area of fusion in the dorsal middle line; in some forms, 
as Siriella, it leaves most of the thoracic segments uncovered. 
The abdomen consists of six segments and a telson; the 
first five abdominal appendages in the female are usually small, 
