ink sac (English spelling) inksac

…the ink sac is an organ unique to the cephalopod mollusks. It is located in the ink sac, just behind the anus above the rectum, and is a gland that secretes ink (commonly known as squid ink). The ink sac is dropper-shaped, and the ink duct (ink duct) has two sphincters near the opening to control the discharge of ink.

*Some of the terminology that mentions "ink sac" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…軟体動物頭足類特有の器官で，直腸上の肛門のすぐ背側にある墨汁囊ink sac中にあって墨汁ink(いわゆるイカの墨)を分泌する腺。墨汁囊はスポイト状で，輸管(墨汁管)には開口近くに括約筋が二つあって墨汁の排出を制御できる。…

※「ink sac」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報