umerous spines of various lengths, which
must afford some protection to the males, rudely arranged in lines,
parallel to the edge of the valve, indicating the successively-formed
layers of chitine; each spine has a fine, tortuous tubulus connecting
its base with the underlying corium. The extreme outer edge of the
border is thin, forming a kind of lip, close beneath which the delicate
tunic lining the sack is attached. During continued growth, the valve is
added to in thickness, and so is the chitine border, and likewise in
breadth. It appears that the larva of the male must attach itself on the
under side of this border, on the edge of the tunic of the sack, and
that by the action of the cement, the corium beneath is killed (as I
believe always is the case with other parasitic Cirripedia), whereas on
both sides, the chitine continues to be added to, so that the male,
excepting the upper and always projecting portion, becomes imbedded at
first laterally, and ultimately all round: I have seen specimens in
several different stages of imbedment. Hence, in old specimens, with a
thick and broad chitine border, it might and does come to pass that one
male is imbedded (the valve being laid flat) directly beneath another.

I have examined a great number of specimens from various localities,
taken at different times of the year,--some dozen specimens from
Cornwall,[53] and several from unknown localities in various
collections; some from Ireland, from the Shetland Islands, from Norway,
and from near Naples. Every one of these specimens, with the exception
of some of the Neapolitan ones, had parasitic males attached to them: I
must also except very young specimens, on which they never occur. On a
Cornish specimen, with a capitulum a little more than one fifth of an
inch in length, it may be mentioned as unusual that there were three
males. In young specimens there is generally one male on each scutum,
but sometimes there are two, and sometimes none on one side. In large
old Cornish specimens I have counted on the two sides together, six,
seven, and eight males, and in one Irish specimen no less than ten,
seven all close together on one valve and three on the other, but I do
not suppose that all these were alive at the same time. In the
Neapolitan specimens, however, which are the largest that I have seen,
there was in no case more than two; and out of seven or eight
specimens, four had not any male; so that it would appear there i