CCELENTERATES. 



27 



stated that the Yelelloe float on the surface, the sail being influenced by 

 the wind. Whether this ever occurs is a question, since naturalists have 

 always found it capsized, the *• sail " in reality forming a keel to catch 

 the currents of the water. 



Still another group of jelly-fishes are the so-called Ctenophores (comb- 

 bearers), which derive their name from the rows of comb-like vibratile 

 cilia found on the surface of the bod}*. These are 

 shown in the adjacent cut of a portion of one of the 

 species found on our coast. The whole animal is shown 

 in the plate facing page 28. These jelly-fish are much 

 more complex in their structure than any of those 

 which we have passed. Here, as among them, there is 

 considerable diversity in form. Some lack the long 

 trailing tentacles of the form figured in the plate ; some 



spherical, some with a very marked bilateral sym- 

 metry, even with wing-like processes extending from 

 either side, making one think, as he views them, of the 

 cherubs on the tombstones of some old cemetery ; some 

 are delicately colored, some as limpid and translucent 

 as the water in which they live, but of all none can 

 compare for peculiar form with the Venus' s girdle, of 



which a figure is here given. Imagine a ribbon of 



Fig 



28. — A Ctenophore 

 i I'h urobrachia ), with 

 only a portion of the 

 tentacles; at c are the 

 rn\v< of " combs," from 

 which the name of the 

 group is derived. 



transparent gelatine five feet in length, two inches or 

 more wide, its edges with cilia, and with a mouth half- 

 way between the two ends, the wdiole coiling and un- 

 coiling gracefully, while the cilia keep up a constant 

 motion, and you have a vague conception of this the most curious of all 

 the jelly-fishes. 



In treating of any group of the animal kingdom, it is impossible to 

 follow straight lines, for none exist in nature. It is like climbing a tn e. 

 We follow^ one branch to its tip, then descend to the next branch and 

 follow that out. But when we put our account on paper we are con- 

 strained to follow a linear arrangement, hut it must be understood that 

 this does not indicate a similar arrangement in nature. For instance, we 

 have just followed out the groups of jelly-fishes to the end. We now 

 descend to the main trunk, and follow out another limb of the zoological 

 tree. 



Of all the animals so far described, the hydra is the most similar to 

 the sea-anemones and the corals, the group of coelenterate animals now to 

 be taken up. To be sure, there are many and important points of differ- 

 ence, but with these we need not trouble ourselves. All chat needs descrip- 



