Survey of the Animal Kingdom 291 



Phylum 4. Ctenophora (te-nof'ora) (Gr. ktenos, comb; phoreo, to bear) 

 General Characteristics 



Ctenophores are jellyfish-like marine animals which are found in warm seas. 

 They are free swimming because of eight bands of vibratile swimming plates com- 

 posed of rows of fused cilia radially arranged. Many Ctenophores possess solid, 

 contractile tentacles. Beroe sp. (Fig. 97) is an exception. With one exception, 

 Ctenophores possess no nematocysts (stinging hairs). Ctenophores are nearly 



Fig, 95. — Sea anemone (Metridium sp.) of the phylum Coelenterata, class 

 Anthozoa, dissected to show internal structures. 1, Siphonoglyphe or ciliated 

 groove in the side of gullet; 2, tentacle; 3, inner ostium through which water 

 passes; 4, outer ostium; 5, ring muscle; 6, ectoderm; 7, entoderm; 8, gullet; 9, 

 primary mesentery extending from gullet to the body wall; 10, cinclides or spe- 

 cial apertures in body wall; 11, gastrovascular cavity or radial chambers, six in 

 number; 12, mesenteric filament; 13, acontia or special threads armed with 

 nematocysts (acontia may be protruded through the mouth or cinclides) ; 14, 

 secondary mesentery; 15, tertiary mesentery; 16, retractor, muscle; 17, gonads or 

 sex organs (diecious) ; 18, directive mesenteries, one pair at each end of the 

 gullet (stomodaeum), opposite the siphonoglyphe, having their longitudinal mus- 

 cles turned away from one another; 19, basal disk (Copyright by General Bio- 

 logical Supply House, Inc., Chicago.) 



