110 LOWER INVERTEBRATES. 



animal, but in Ocyroe these lateral develoisments take on the form of wings or similar 

 bodies. Cestiis moves through the water by a slight undulation of the body, while 

 Ocyroe does the same by a flapping movement of its greatly developed lateral lobes, 

 and by their beating upon the surrounding water. When Ocyroe is at rest, the lateral 

 wings are widely extended, giving to the animal a remote likeness to Cesttts. When, 

 however, motion is attempted, the lobes are raised above the horizontally extended 

 position whicli they occupy at rest, and then violently swung downward, passing 

 through almost 180°. This flapping of the two wings in concert is continued several 

 times, and in that way the animal is propelled through the water. The function of 

 the rows of combs in the movements of the medusa is secondary to the flapping move- 

 ments of the lateral wings. 



The body of Ocyroe, from two sides of which the wings arise, is of oblong, oval 

 shape, with a mouth at one pole, and a cluster of otoliths in an otocyst at the opjiosite. 

 There is no vestige of tentacular appendages near the mouth, and the lips are undi- 



vided, smooth, and highly flexible. Ocyroe thus far has been taken only from the 

 waters of tropical America. 



In colder latitudes as on our New England coast, we have a beautiful ctenophore 

 called Jiolina, and another very closely allied genus known as Mueniio2}sis. These 

 medusfe are in many respects most closely allied to Ocyroe, or rather Ocyroe seems an 

 aberrant form of these more northern jelly-fishes. Although the same lateral lolies 

 exist in both genera, their importance in Bolina, as far as movement is concerned, is 

 much less than in Ocyroe. They are also seldom or never carried extended horizon- 

 tally at right angles to the body, as in the curious genus Ocyroe. Holiria is one of the 

 most transparent of the comb-bearing medusie. The body is very gelatinous and 

 highly phosjjliorescent. The sides of the body are developed into two larger lappets or 

 lobes which are carried or hang vertically instead of horizontally. On account of the 

 contractile powers of the body walls, Molina can vary its outlines very considerably ; as 

 a rule, however, when the body is seen from the side, it has an oval or elongated form. 

 Eight rows of vibratile combs contribute to the jiropulsion of the medusa through the 

 water. These lie upon the external surface of the body, and arising from the pole 

 opposite the mouth-opening, extend to the more distal edge of the lateral expansions 

 to the vicinity of the mouth. From the great development of the lateral lobes, the 

 four lines of vibratile condjs which cross these bodies are much longer than those 

 which lie on the body regions between them. Two tentacles are found hanging from 

 the sides of the body of Boluia. These tentacles are of diminutive size in the adult, 

 and are remnants of structures which in early conditions of growth were very much 

 more developed. 



