ANCEUS. 185 
of correctness, is the earliest stage in all crustaceous 
life. The ova are proportionately very large, and the 
parent retains the young after it has quitted the egg, 
until the young animal is scarcely less than half the 
length of the parent. M. Hesse has figured a speci- 
men, in which he has represented all the larve placed 
within the ovi-pouch in a uniform manner, the head of 
each being directed towards the centre of the pouch ; 
this is not in-accordance with our observations, as, of 
the number of specimens that we have seen carrying 
young, we have found all with the young creatures 
variously placed, some with the head, others with the 
tail, directed forwards or across. When the young quit 
the care of the parent, nothing but a thin, transparent 
skin remains, and the parent probably dies. 
The male differs from the female by the presence of a 
remarkable pair of mandibles directed forwards; fierce 
and terrible organs of prehension they must be, but they 
have always struck us as being organs that must be 
valueless in assisting the animal in feeding. After we 
had observed the structure of the oral organs of the 
female, we directed our attention to those of the male. 
In A. mazillaris,* on the under surface of the head, exists 
a pair of large two-jointed plates, the basal being sub- 
triangular and large, the other small and apical. From 
its position and structure we consider this as the 
representative of the hooked appendage in the young 
animal, consequently the homologue of one of the pairs 
of gnathopoda; beneath this lies a pair of foot-jaws, in 
form very closely resembling those of the adult female. 
On removing these, we arrive at a crustaceous surface, 
with a minute and apparently imperforated tubercle in 
* See the various details of the underside of the head and its organs 
represented in p. 190. 
