Cirripedia , Barnacles. 
33 
cipes may be noted as having rows of valves on the capitulum 
which pass gradually into the small scales covering the peduncle. 
These scales appear to be the remains of a shelly armour covering 
the peduncle which was more fully developed in certain extinct 
genera, and is shown in the casts of the fossil Loricula and Turri- 
lepas exhibited in this case. The genus Scalpellum is of interest 
not only on account of the deep-sea habitat of many species and 
the great size of some (Scalpellum giganteum), but also and more 
especially because of the dwarf male individuals already alluded to, 
which are found in this genus and in the related Ibla. In the 
different species of Scalpellum three conditions are represented. 
In some, all the individuals of a species are similar and hermaphro- 
dite as in ordinary barnacles ; in others, as in Scalpellum peronii, 
of which a specimen is shown, the large hermaphrodite individuals 
have small males attached to them like parasites ; in others again 
the separation of the sexes is complete and the larger individuals 
are purely female. 
Most barnacles are hatched from the egg as actively swimming 
larvae of a type which is found in many other Crustacea, and is 
known as the Nauplius. They have three pairs of appendages, an 
unsegmented body, and a conspicuous median eye. Like many 
other “ pelagic ” animals the Nauplii of barnacles living at the 
surface of the ocean often have long spines and outgrowths 
from the surface of the body, which are probably of service in 
keeping the animals afloat. A~ coloured drawing of one of these 
spiny larvae is exhibited. In its later development the young 
barnacle passes into a stage in which the body and limbs are 
enclosed in a bivalved shell like an Ostracod. On account of this 
resemblance the stage is known as the “ Cypris ” stage, after one 
of the genera of Ostracoda. After swimming about for some time 
longer it attaches itself by means of its antennules, casts off 
its bivalved shell, and gradually assumes the structure of the 
adult. 
The Sessile Barnacles or Acorn-shells, forming the sub-order 
Operculata (Fig. 13b), agree in most points of structure and 
development with the stalked barnacles, but they have no peduncle. 
The shelly plates of the mantle are, for the most part, soldered 
together to form a cylindrical or conical case, the opening of which 
is protected by four movable “ opercular ” plates. In a preparation 
of Gatophragmus polymerus here exhibited, names are attached to 
those parts of the shell which are found (though often reduced iu 
number by coalescence) in all the typical Operculata, the “ scutum ” 
D 
Table-case 
No. 3. 
