from
The Collaborative International Dictionary of English v.0.48
Hectocotylus \Hec`to*cot"y*lus\, n.; pl. {Hectocotyli}. [NL.,
fr. Gr. ? a hundred + ? a hollow vessel.] (Zool.)
One of the arms of the male of most kinds of cephalopods,
which is specially modified in various ways to effect the
fertilization of the eggs. In a special sense, the greatly
modified arm of Argonauta and allied genera, which, after
receiving the spermatophores, becomes detached from the male,
and attaches itself to the female for reproductive purposes.
[1913 Webster]