132 



CCELENTEEATA 



Class 3. ANTHOZOA. (Actinozoa.) 



Fig. 219 — Diagram of a longitudinal 

 section of a coral animal (Boas). 1, ten- 

 tacle ; 2, mouth ; 3, gullet; 4, mesentery ; 

 5, base of a mesentery which has been cut 

 away ; 6, septum of the calcareous skele- 

 ton covered by a fold of the foot ; 7, theca; 

 8, septum. 



Corals, sea anemones, etc. Coe- 

 lenterates in which the polyp form 

 alone is present, no medusa gener- 

 ation appearing'. The body (Fig. 

 219) is usually cylindrical in form 

 and is attached either permanently 

 or temporarily at one end, which, 

 in the sea anemones, is called the 

 foot or pedal disc. The other and 

 flattened end is the oral disc; in its 

 center is the mouth surrounded by 

 hollow tentacles, which may num- 

 ber from six to several hundred. 

 The mouth is not round, but an 

 elongated slit, at one or both ends 

 of which is a prominent, ciliated 

 groove called the siphonoglyph, through which the genital products may 

 roach the outside (Fig. 220). The mouth does not lead directly into the 

 gastrovascular space, but into a 

 tube lined with ectoderm called the 

 gullet which opens into the gastro- 

 vascular cavity below. This cavity 

 is divided into a number of com- 

 municating chambers by six or 

 more wide longitudinal ridges called 

 the mesenteries, which spring from 

 the body wall and project towards 

 the center of the cavity; in the 

 upper portion of the body, certain 

 of these mesenteries johi the body 

 wall with the wall of the gullet 

 (Fig. 220), thus dividing this part 

 of the gastrovascular space into 

 small chambers which are continued 

 above in the hollow tentacles, while 

 in the lower portion of the gastro- 

 vascular space the edges of the mes- 

 enteries are free. 



Along the free edge of each mesentery is a convoluted thickening, the 

 mesenterial filament, which is of great importance inasmuch as it contains 



Fig. 220 — Diagram of a cross section 

 of an authozoan through the gullet 

 (Weysse). 1, siphonoglyph; 2, gullet; 

 3, primary mesenteries ; 4, secondary 

 mesenteries ; 5, tertiary mesenteries ; 6, 

 longitudinal muscle. 



