484 On the Nauplius Stage of Prawns. 
near the frontal margin was seen an opaque mass of minutely 
eranulose texture, and extending beyond it a small round tu- 
bercle. The same is observable in the youngest Zoéa. From 
this mass are developed at a later period the paired eyes ; 
and on them the tubercle is retained as far as the Mysis stage 
(fig. 9,0). I know of no other Crustacean with any such 
tubercle. 
And with all these points of resemblance, what then are the 
differences? That the Zoéa is a little larger—that the cara- 
pace, already indicated in the Nauplius, is well developed— 
that the feet present as rudiments have come into action— 
that a few new sete have been added,—steps in advance, 
every one of which might have been predicted. 
Ishould have supposed that these reasons would pretty well 
suffice to convince the most obstinate doubters. However, if 
my Nauplius be not derived from a Peneus, and is not to 
become a Penceus, let them tell me what possibly it can be. 
The child must surely have a father. Still less than to the 
prawns would one assign it to any other Crustacean of the 
Malacostracous division, whether a crab or a woodlouse. 
Considering that the Phyllopods are wanting in our seas, 
there remain but the Copepoda, with the Lernzans, and the 
Cirripedes, with the Rhizocephala as the possible termination 
of its development. 
It is impossible for it to become a Cirripede or a Rhizo- 
cephalan; the formation of the heart, liver, and mandibles 
suffice to demonstrate this. In addition it wants the frontal 
horns of the Cirripede-larvee, as well as the spines (Zacken) 
and teeth, with which the third pair of limbs of the Nauplius 
of the Cirripedes is armed. When near passing into a second 
developmental stage, as the Nauplius represented in fig. 2 (J. c.) 
is, we should see in a Cirripede or Rhizocephalan six new 
pairs of feet under the skin, but not four of them sprouting 
torth freely on the ventral surface &c. It resembles certain 
Nauplius-forms of the Copepoda much more than those of the 
Cirripedes. In these also there occur stages of development 
in which, besides the three original pairs of limbs, rudiments 
of four new pairs are to be seen. But Ido not know from my 
own experience, nor can I find among the numerous figures 
which adorn Claus’s admirable work on the Copepoda, any 
form of mandible which could be compared to that of 
our Nauplius. Moreover, in all the marine Copepoda except 
the Coryceide, the third pair of limbs remain a well-bristled 
mandibular appendage. But, apart from this, the Corycexide 
have no heart such as our Nauplius possesses. 'To this we 
must add that the Nauplius reaches the length of half a 
