Introduction to Afiimal Morphology. 95 



sessile unilateral hydrotheca, scattered degraded hydranths, 

 consisting of cup-like cavities of the perisarc filled with pro- 

 toplasm, in which nettle-cells are embedded, forming nettle- 

 batteries or nematophores, for the protection of the colony ', 

 gonozooids fixed,* simple, axillary, ex. Plumularia. 



Order 4. Monopsea [Allman) — Possibly only a pro- 

 visional order, including those forms with no known 

 trophosome separate from blastochemes, and in which 

 the medusae develop directly from the Q'g^. 



Four families are included : — 



I. Geryonidse — manubrium elongated ; lithocysts inter- 

 tentacular ; sex-organs in flat masses along the radial canals, 

 which may be four (Liriopinas) or six (Geryoninae) ; in the 

 former there are no centripetal canals, often a tongue-like 

 process, and eight (Xanthea) or four tentacles (Liriope) ; or 

 no tongue-like process, and eight (Glossoconus) or four ten- 

 tacles (Glossocodon). In the latter there are many blind 

 centripetal canals, with (Carmarina, Fig. 12, E), or without a 

 central tongue-like process (Geryonia), except in Leuckartia, 

 where these canals are absent. 2. vEginidse — disc with 

 tentacles springing above the margin ; radial canals, pouch- 

 like, wide 4-32; lithocysts marginal; Cunina has simple 

 tentacles, each with a conical cartilage at the base, springing 

 opposite the stomach pouches (in ^gina they alternate), and 

 a broad simple mouth, ^ginopsis, which has oral tentacles, 

 has been traced from its &g^ with no trophosome stage. 

 Agassiz makes a separate family Brandtidae for allied, but im- 

 perfectly known forms. 3. Trachynemidae — blastochemes 

 with no long manubrium, and stiff tentacles ; disc bell-shaped 

 (Trachynema), or flat (Rhopalonema). 4. Octorchidae — with 

 a solid quadrangular manubrium, having a radial canal at each 

 angle, and eight genital masses, four in the manubrium and 

 four in the sub-umbrella, ex. Octorchis. 



* The protoplasm of the nematophore has been seen to protrude pseu- 

 dopodia (All/nan). These processes are sufficiently constant to be used in 

 classifying the Pfumularice {Kirchcnpauer). Antennaria antennula has no- 

 nettle-cells. 



