Chap, 24 CTENOPHORES COMB JELLIES OR SEA WALNUTS 497 



pharynx and stomach. From there a series of ciliated canals extends through 

 the body, often especially prominent in luminescent individuals (Fig. 24.4). 



Reproduction and Regeneration. All ctenophores are hermaphrodites and 

 in most species eggs and sperm cells are shed into the open water where the 

 eggs are fertilized. 



Ctenophores have high powers of regeneration and can repair severe in- 

 juries to their frail bodies. They have been subjects for many experiments on 

 regeneration and grafting. Any parts removed, including the statocyst, are 

 regrown. Whole rows of combs are replaced. Halves of an animal, cut in 

 either direction, will regenerate but parts containing the statocyst grow more 

 rapidly than others. Pieces of one animal may be grafted into another. Bands 

 of combs may be grafted onto another ctenophore in reverse of their natural 

 position. Such grafted combs will continue to beat as before in opposition to 

 those on the recipient animal, causing the latter to turn round and round. 



Fig. 24.4. Luminescent ctenophores. Beroe photographed by daylight and in 

 darkness except its own light. Vividly shown here are the meridional canals and 

 network of intercommunicating canals. Beroe is less than two inches long and has 

 no tentacles. At certain seasons swarms of ctenophores illuminate wide ex- 

 panses of the seas. (After Panceri. Courtesy, Harvey: Bioluminescence. New 

 York, Academic Press, 1952.) 



