The hydrœcium extends for about half the length of the organ.
1870C.E., Henry Alleyne Nicholson, A Manual Of Zoology, Spottiswoods and Co.; Volume I, Chapter IX, page #81:
The ‘ hydrœcium ’ is formed partially by this chamber in the nectocalyx, and partially by an arched groove prolonged upon the inner surface of the distal nectocalyx, within which the cœnosarc moves freely up and down, and can be entirely retracted if necessary.
1888C.E., Ernst Haeckel, The Voyage of H.M.S. Challenger, in Report on the Scientific Results of the Voyage of H.M.S. Challenger; Zoology Volume XXVIII, page #154:
The funnel‐cavity of the first nectophore, or the hydrœcium, occupies the basal half of its ventral side.
1899–1900C.E., Alexander Agassiz and Alfred Goldsborough Mayer, MEDUSÆ, George M Bowers, Memoirs of the Museum of Comparative Zoölogy; Volume XXVI, №. 2, page #165:
A deep, funnel‐shaped hydrœcium is situated midway between the bell‐cavity and the phyllocyst.
1911C.E., Henry B. Bigelow, Biscayan Plankton Collected During a Cruise of H.M.S ‘Research’, 1900, in The Transactions Of The Linnean Society Of London, Taylor and Francis; Volume XIII, page #349:
The hydrœcium reaches to about the same level as the nectosac, not to the apex as described by Lens and Van Riemsdijk.