it is impossible to believe can be of
any service to the species itself, irrespectively of the lodgment thus
afforded for the males. So again in _S. rutilum_, the shape of the
scutum seems adapted for the reception of the male, in a manner which
must be attributed to its own growth, and not to the pressure or
attachment of a foreign body. Now there is a strong and manifest
improbability in an animal being specially modified to favour the
parasitism of another, though there are innumerable instances in which
parasites take advantage of pre-existing structures in the animals to
which they are attached. On the other hand, there is no greater
improbability in the female being modified for the attachment of the
male, in a class in which all the individuals are attached to some
object, than in the mutual organs of copulation being adapted to each
other throughout the animal kingdom.

Generic Characters of the larval prehensile ANTENNAE, in the Lepadidae,
as far as known from their imperfect state of preservation, and the
number of species examined.

|Name of Species.
| |Length of, from end of disc to the further margin of the
| |oblique basal articulation: Scale, fractions of the 1/6000ths
| |of an inch.
| | |Length of, from end of disc to the inner margin of the
| | |basal articulation. Scale same.
| | | |Width of basal segment, in widest part. Scale same.
| | | | |Disc, length of. Scale same.
| | | | | |Disc, width of. Scale same.
| | | | | | |Ultimate segment, length of. Scale
| | | | | | |same.
| | | | | | | |Ultimate segment, width of.
| | | | | | | |Scale, fractions of the
| | | | | | | |1/20,000ths of an inch.

LEPAS: disc large, thin, almost _circular_, slightly elongated, with
several long spines on the hinder margin; end segment with three very
long, plumose spines on the upper _exterior_ angle.[61]

|_L. anatifera_ (?)
| |62
| | |--
| | | |20
| | | | |23
| | | | | |22
| | | | | | |--
| | | | | | | |--

|_L. australis_,
| |111
| | |--
| | | |40
| | | | |42
|