CRUSTACEA. 
283 
condition of true mandibles. Posterior to tbese^ four pairs of 
lobes have made their appearance upon the ventral surface ; 
these are the embryonic stage of the four next succeeding pairs 
of appendages. The intestine, liver, and heart at this period 
are of the same form as those of the earliest larval condition of 
the Brachyura. The eye still continues to be a solitary central 
organ ; and, concealing it from above, an opaque granular tissue 
has been formed, from which projects a small transparent process, 
to which Dr. Muller fails to assign a purpose. 
The rudimentary appendages exhibit within their several sacs 
the presence of hairs, which induces Dr. Muller to believe that 
after the next succeeding moult they will become effective, 
and pass the animal from its immature stage, to which the 
author has given the name of the Nauplius form, into that which 
assimilates more nearly to that of the larva of the macrurous 
Decapods which are recognized under the general term of Zoea. 
At this stage we have a leap, but certainly not more than we 
meet with in certain other forms of Crustacea which we are accus- 
tomed to recognize as having their development made out. 
The difficulty of preserving the life of these delicate creatures 
has not yet been overcome. The newly hatched larva from the 
commonest, and, we might assume, the hardiest crabs, has not 
been preserved beyond the second stage ; and the link between 
Avhat is termed the larva and the pupa stages of the cirriped has 
not been demonstrated. It is, therefore, not to be demanded 
that Dr. Muller should succeed beyond the step at which others 
have stopped. It is only necessary for him to show assimilation 
of conditions to enable us to accept his conclusions. 
In the next stage the larva has about doubled its length, and 
it is during this period that the two eyes are developed ; ten or 
eleven new somites are formed, with a pair of appendages at- 
tached to the first, and the rudiments of appendages to the five 
succeeding, as well as the lateral caudal appendages to the pen- 
ultimate somite of the pleon. These several parts vary some- 
what in form ; but in other respects the animal undergoes no 
important changes, even in size, except length, which is almost 
exclusively due to the gradual extension of the eleven new 
somites. 
The carapace, from 0*4 to 0*5 mill, long, at first is almost 
circular and flat, but soon it bends laterally downwards and 
covers the basal portions of the anterior appendages, and projects 
posteriorly over two or three of the newly-formed somites. 
Anteriorly it is at first hid by the contiguous newly-developed 
organs of vision. When these separate, it covers and protects 
the base of the ocular peduncle with a triangular process that 
runs out into a spine, that reaches to the length of O’ 12 mill. 
The ear apace has no other spiniform process. Between these 
two eyes, now in the progress of development, and beneath and 
