hectocotylus
noun
hec·to·cot·y·lus
-ᵊləs
plural hectocotyli
-ᵊlˌī
: a modified arm of a male cephalopod that is specially and variously adapted to effect the fertilization of the eggs
especially : an arm that in argonauts and some octopods receives the spermatophores, is inserted into the female mantle cavity, and then is broken free from the body of the male
Word History
Etymology
New Latin, from hect- + -cotylus (from Greek kotylē cup, anything hollow)