114 Introduction to Animal Morphology. 



China Sea they have been found up to three feet in 

 diameter, and containing Clupeoid fishes as com- 

 mensals [Collingtvood). 



Three families exist: — i. Zoanthidce — the only colonial 

 forms, with a creeping, leathery, filiform, spiculigerous 

 coenosarc ; zooids united by a flat, root-like mass of stolons 

 (Palythoa), or by basilar budding (Zoanthus). The tentacles 

 are in several cycles, each one communicating with one 

 segment of the perivisceral cavity. Foreign bodies may be 

 enclosed in the ccenosarc (Heterozoanthus). 



2. Cerianthidse — hermaphrodite ; with no spicules ; ten- 

 . tacles in two concentric circles, not alternate, two communi- 

 cating with each intermesenteric space. The mesenteries 

 do not extend to the hinder end, and in the young there are 

 only four. The aboral end is pointed, perforate (Cerianthus), 

 or imperforate (Saccanthus). In the former, two mesenteries 

 extend farther than the others, and a deep, gutter-like groove 

 continues along its body cavity to its foot. It throws off a 

 slough of thread cells and mucus, mixed with foreign bodies. 

 Saccanthus has equal mesenteries. 



3. Actiniidae — separate personce, with many series of ten- 

 tacles ; stomach with two lateral grooves (cartilaginous in 

 Sphenopus). This includes four sub-families : — Minyadinae — 

 having the foot dilated into a rounded air-holding sac ; the 

 body may be warted (Minyas) or smooth, with simple 

 (Plotactis) or lobed tentacles (Nautactis). Actininae — foot 

 with a muscular sole (sucking disc) ; tentacles conical, often 

 uniform, not retractile (Anthea) or retractile (Actinia). The 

 mouth may have two long lips (Actinopsis), or several crispate 

 lobes (JMetridium), or a trifid lip (Siphonactinia). A few are 

 rounded, or pointed distally, and free swimming ; of these, 

 Peachia and Halcacampa have a distal perforation. Milnea 

 and Arachnactis are rounded, and the former has a median 

 epidermic girdle ; Ilyanthus is pointed, imperforate ; cinclides 

 are numerous, and often wart-like in Cribrina, Sagartia, 

 Adamsia, &c. Phyllactinse — tentacles both simple and lobate, 

 the latter in an outer cycle (Phyllactis), or between two series 

 of simple ones (Rhodactis). Ulactis has a warted body. 



