Nauplius Stage of Prawns. 483 
an older Nauplius whose third pair of legs I drew in fig. 3 
(in four specimens), and one younger Zoéu. 
But as it is just against this point, and, as far as I know, 
against this point exclusively, 2. e. against the relation of the 
Nauplius with the Zoéa, that the doubts are directed of those 
who cannot believe in the metamorphosis of a auplius into a 
long-tailed crustacean, | will once more place together the 
peculiarities in which the oldest Nauplius agrees with the 
youngest Zoéa. 
In the first place, they have the same highly peculiar mode 
of movement, by which they are distinguished at once from 
all other marine Crustacea. 
In the second place, they have the same colour. The two 
anterior pairs of limbs and the fork-like caudal extremity 
especially show a peculiar brown colour deepening towards 
the extremity, which I do not find in any other Crustacea 
of our sea. 
In the third place, the proportional length and the whole 
appearance of the first two pairs of limbs are the same; only 
they are more distinctly articulated in the Zoéa, and the second 
pair is more profusely ciliated: instead of three hairs on the 
end of the inner branch, there are four. Likewise the posterior 
extremity of the Zoéa differs only in having the two branches 
further asunder, and in having first seven and still later eight 
hairs on each branch, instead of six as in the oldest Nauplius. 
In the fourth place, trom the structure of the third pair of 
limbs (fig. 8) of the oldest Nauwplius it is evident that after 
the next change of skin it must have mandibles with an 
acute, prominent tooth, and a broad, transversely furrowed 
masticatory surface, and that the mandible must bear a dark 
brown, non-setigerous appendage. The youngest has such a 
mandible, and bears such an appendage; and it may be re- 
marked that the Nauplius was observed on the 24th of 
January, and the Zoéa on the 3rd of January, when I had 
no idea of the significance of this appendage to the mandible. 
I am acquainted with no similar appendage in any other 
Crustacean, young or old. 
In the fitth place, we see in (¢. e. from the structure of) the 
oldest Nauplius, that the next stage of development must 
possess four more pairs of limbs; the youngest Zoéa does 
possess four more pairs of limbs, corresponding in form to the 
rudiments present in the Nauplius. 
In the sixth place, the formation of the heart, intestines, 
and liver is exactly the same in the oldest Nauplius and 
youngest Zoéa, 
In the seventh place, in the oldest Nauplius, on each side 
