418 
Proceedings of Boyal Society of Edinburgh. [jult 2, 
almost exactly similar Nauplius belongs to these two forms, are 
questions which must be left to the future to decide. 
The following is a summary of the metamorphosis of the group : — 
1. NaupUus . — Body oval, unsegmented; median unpaired eye. 
Three pairs of limbs only : — 
1st, antennules (long) simple. 
l*\i nrt /*\TT a in r» rtir/nitr-T 
2. This simple condition is followed by a second Nauplius stage, 
in which the three pairs of appendages are retained, and in 
rudiments. 
Between this stage and the next to be described a gap 
exists in our record, which probably does not extend over 
one or two moults. 
3. Metanauplius . — Body nearly as in Nauplius stage, but the cara- 
pace has made its appearance as a dorsal and lateral thicken- 
ing of the epidermis. Only two pairs of appendages are 
developed (1st and 2nd antennae); mandibular legs lost. 
Mandibles, maxillae, and maxillipeds present as buds only. 
Commencing elongation of the posterior portion of the body 
to form the trunk. 
4. Calyptopis . — Body divided into two regions — cephalo-thorax 
and abdomen. Carapace distinct, forming anteriorly a hood- 
like expansion. Tail becoming segmented. Compound 
eyes undergoing development under the anterior portion of 
carapace — still immobile. Mandibles, maxillae, and maxilli- 
peds distinct, but no trace of legs or pleopods. Uropods 
becoming developed. 
This stage is represented by four moults at least, during 
which the abdomen elongates and becomes segmented, and 
the uropods become developed. 
5. We find the Calyptopis stage to be followed by an inter- 
mediate stage, which links it to the Burcilia type, which has 
the eyes exposed on each side of the rostrum. 
During this stage the antero-lateral margins of the hood- 
like expansion of the carapace become absorbed, leaving the 
rostrum in the median dorsal line as a portion of the anterior 
biramous — natatory. 
addition the maxillae and maxillipeds exist as bud-like 
