Dr. F. Miiller on the Metamorphoses of the Prawns. — 105 
mediate feet have two bristles at the apex of the anterior branch, 
and six on the anterior margin and apex of the posterior branch ; 
and each branch of the posterior feet has two bristles at its apex 
and one below this point. 
The little animal is rather opaque, and of a brownish colour, 
which is more strongly marked at the apices of the feet. The 
structure of the mouth and of the internal organs was not ob- 
served, 
The somewhat flexible feet, with their few long bristles, form 
no very effective motory apparatus. A man floating perpendi- 
cularly in the water, with widespread arms and slender willow- 
branches in each hand, striving to work himself upward, would 
furnish a notion of the peculiar movement by which this Nauplius 
and the Zoéa proceeding from it may be recognized at the first 
glance amongst hundreds of other small Crustacea*. 
In a rather larger larva (0°5 mill. in length), taken on the 
13th of January, which agreed in the general form of the body, 
in the structure of the feet, and in colour with the preceding 
one, the posterior extremity was drawn out into two thick conical 
processes, at the apices of which stood the two long caudal 
bristles, each accompanied on the inside by two and on the 
outside by three shorter and partly spiniform bristles. The 
number of bristles on the ‘intermediate feet had also increased. 
As the first indication of the carapace, a transverse fold ran 
across the back, nearly in the middle of the body. The poste- 
rior feet were placed more anteriorly and nearer the median 
line, towards the mouth, which is situated between them ; be- 
‘fore the mouth, between the intermediate feet, was a large helmet- 
shaped upper lip. The short stem of these feet had become 
thickened almost into a globular form; some new part was 
evidently being formed in its interior, the outlines of which, 
however, were not yet distinct. Behind the mouth, and filling 
the median third of the body, four pairs of long and plump 
lobes had sprouted from the ventral surface, and, inclining 
backwards, had applied themselves to the body. In the form of 
the first two pairs the future lower jaws could already be re- 
cognized. 
This larva is closely approached by four others, probably be- 
longing to the same swarm, which were taken at the same time 
(24th of January). In the swelling at the base of the posterior 
* From this peculiar movement, observed with the naked eye, I recog- 
nized the little animal just described as the larva of Peneus ; microscopic 
examination made this opinion appear, if not erroneous, at least extremely 
improbable. A month later, intermediate forms occurred which showed 
the naked eye to have been right, im opposition to the microscope; the 
latter alone would probably never have led me to suspect the true nature 
of my Nauplius. 
