GENERAL CHARACTERS. 
7 
anterior (h, i, k 3 1 ), and in some genera the fifth (m,) pairs 
of limbs, these plates are much larger than in the three 
or two posterior pairs ; hut to compensate for this diminu- 
tion of size, the three posterior (m, n , o), with few generic 
exceptions, have the second joint produced posteriorly 
into a large and squamiform plate. In Caprella and the 
allied genera, the first joint of each leg is fused with the 
body of the animal, and is never shaped like scales. 
The five posterior pairs of legs (pereiopoda, k-o) are 
the walking appendages ; they homologize with the ten 
legs in the Decapoda, and as efficiently fulfil their design. 
Like them, they consist of seven joints; hut, unlike 
them, all articulate in planes vertical to the body of 
the animal, having no lateral movements. The two ante- 
rior pairs of walking legs are directed forwards, and the 
three posterior are directed backwards. Thus the seven 
pairs of legs constitute three distinct series, generally 
differing from each other in their proportions, size, and 
direction, the first and second pairs being subcheliferous, 
the third and fourth porrected, and the fifth, sixth, and 
seventli pairs directed backwards. 
The branchiae ( 1 ") consist of a series of vesicles ; a 
single sac being attached to, and pendent from, the first 
joint of all the legs except the first, and in the males of 
some genera also the last. 
The ova are nurtured within a pouch formed by a 
series of foliaceous plates (l'"), one of which is attached 
to the first joint of the four anterior pairs of legs in 
females. In this pouch the embryo continues until it 
has arrived at a period when there is but a slight dis- 
tinction in form between it and the parent, except in 
the Hyperina, as has been shown by Miln e-Edwards 
and Gosse, where the form of the young animal differs 
considerably from that of the parent. 
Posterior to the legs used for walking, are three pairs 
