118 



HYDEOZOA. 



Fig. 56. 



the disk ; the oral aperture, instead of being pedunculated, is simply 

 surrounded with a mem- 

 branous border, hanging 

 loosely down when in a 

 state of repose, and so 

 short as to be quite in- 

 adequate to close the 

 opening of the mouth. 

 Superiorly this membra- 

 nous border is attached 

 to a ring, slightly more 

 callous in its structure 

 than the rest of the body, 

 immediately above which 

 is a circle of tolerably 

 wide orifices placed very 

 close to each other, all 

 of which lead into radi- 

 ating canals that diverge 

 towards the circumfe- 

 rence of the disk. These 

 canals, seventy-four in 

 number, becoming narrower as they 

 recede from the stomachal cavity, run 

 in straight lines to terminate in a 

 circular vessel that surrounds the disk 

 near its margin, from which little 

 canals are given off, apparently ana- 

 logous to the emunctory vessels above 

 described as existing in Medusa aurita. 

 (307.) The generative system in 

 JEquorea is in relation with this 

 arrangement of the nutritive canals. 

 Arising from the under surface of the 

 disk there are numerous membranous 

 lamellse disposed in a radiating man- 

 ner around the gastric cavity. These 

 Iamella3 seem to be suspended from 

 beneath each radiating canal; con- 

 sequently they are seventy-four in 

 number; and being much folded upon 

 themselves, each has the appearance 

 of being formed of a double mem- 

 brane. In their interior they exhibit 



Young Medusa (after Sars). a, the mouth, surrounded 

 with the as yet undeveloped buccal arms ; 6666, ovaria, or 

 testes ; c, radiating nutritive canals ; d, marginal circle of nu- 

 trient vessels ; e, oculiform organs ; fff, anal apertures situ- 

 ated on the margin of the disk. 



Fig. 57. 



1, 2. Cuvieria carisochroma. 



numerous striae of a violet hue, which the microscope shows to con- 



