MEDUSAE. 709 



as their parent* But germination is carried on naturally by buds thrown 

 out, and cast (by " gemmation "), or by the ordinary sexual production 

 of ova. 



The outer and inner skins of the hydra are called the ectoderm and 

 endoderm, andthe animal is quite capable of locomotion, walking, or rather 

 moving, backwards, by raising and planting its sucker or foot, and by 

 swimming. The prey is captured by the tentacles and by the darting out 

 of tiny spears from the cells or " thread cells " which contain them on the 

 surface of the body. The well-known " Portuguese man-of-war," an ocean 

 polype, has these " harpoons " greatly developed, and can inflict serious pain 

 as of many stinging nettles ; the sensation is 

 exceedingly painful, and lasts some time. 



The MEDUSID^ are known to the seaside 

 visitor as the jelly-fish, and the other Acalepha, 

 the " hidden-eyed" medusae, include the Portu- 

 guese man-of-war mentioned above, and many 

 other umbrella-like animals. They have re- 

 ceived the name of medusae from Medusa, 

 whose long, snaky locks the tentacles of the 

 animals are supposed to be like. Some of 

 these " floating umbrellas " are very dangerous, 

 and will inflict severe stings upon any one in 

 their vicinity. The tentacles or filaments 

 extend for a long distance, and bathers should 

 be cautious. We have often watched them, 

 and they are beautiful to contemplate particu- 

 larly at night, and in Kingstown Harbour, 



J T^ i ,. & ,. t Fig. 833-- Medusa. 



near Dublin, many exceedingly fine specimens 



have been obtained, The pulsation of the " umbrella " or bell, enables the 

 animal to swim, and the even undulations of this beautiful covering are 

 apparently caused by nervous contractions. 



The jelly-fish have no resemblance to " fish," and scarcely appear to 

 exist ; they are of no use to man, and when removed from the water dwindle 

 by little and little to a tiny film-hind nothing more they dissolve into air 

 and water. Cases have been known and tales told of how farmers collected 

 hundreds of these jelly-fish for manure, and when the cart reached the field, 

 to the man's astonishment, nothing was left but what appeared cobweb in 

 the place of the load of fish. 



The Cydippe is a very common specimen, and moves by means of its 

 cilia ; Cesium Vcncris the zone or girdle of Venus is another curious 

 example. It appears like a glass ribbon about five inches wide and perhaps 

 four or five feet long. The cilia when in motion are very brilliant in 



* Hercules conquered the " Hydra," which is represented in mythology as capable of 

 reproducing two heads for each one cut off by the warrior. 



