SCYPHOMEDUS.E OF THE AUSTRALIAN SEAS. 11 



instance phylogenetically like the nervous elements from the ectodermal 

 epithelium only, and situated in the sub-epithelium. The surface is folded so 

 as to increase the extent and power of this muscular lamella, the projecting 

 ribs are tough and elastic, and act like springs, inasmuch as they counteract 

 the effect of the muscular contraction. The muscles are situated in very 

 regular fields ; there are circular and radial muscles. All are composed of 

 band-shaped striated fibrils. By their contraction the umbrella is more 

 curved, and when the contraction ceases the umbrella is again flattened out 

 by the elasticity of the ribs mentioned above. By this movement of the 

 umbrella the animal propels itself through the water. It is apparent that 

 this apparatus for locomotion is not a very satisfactory one, and the move- 

 ment, which appears most graceful but rather languid, results in a very slow 

 motion of the animal through the water accordingly. 



5. The stomach has more or less the shape of a very flat lens. From its 

 margin canals arise, which sometimes form networks, and which supply the 

 margin of the umbrella with nourishing material. The surface in which these 

 canals are situated is marked by a lamella of entodermal cells the ento- 

 dermal lamella, which extends throughout the umbrella, dividing into two 

 parts a thick upper part without appendages, the ex-umbrella, and a thin 

 oval part. In all the vital organs are situated the sub-umbi-ella. The stomach 

 and canals are clothed with ciliated and gland cells of intodermal origin. By 

 the continued vibration of the cilia, the contents of the gastro-vascular 

 cavity are kept in incessant circulation. The Scyphomedusre do not eat any 

 large animals, biit only soft and tender organisms like themselves. 



6. The sub-umbral wall contains in four localities in the secondary radii 

 appendages to the gastral cavity. In the walls of these the sexual products 

 are matured. The outer shape of these genital organs is subject to great 

 variations. They are generally very brilliantly coloured at the time when the 

 sexual products are ripening in them. The latter have been described above. 

 Often the four sexual organs of the secondary radii divide. Then there are 

 eight which occupy the tertiary radii. 



7. Generally the mouth is situated at the lower side in the middle of the 

 stomach, and is cross-shaped. The margin of the mouth is produced in all 

 the ScyphomeduscT, with the exception of the Rhizostomse, where different 

 structures are met with, to form lips. These may attain a very high degree of 

 development, and grow out to form a long tube or large lamellons,* or mem- 

 branes extensions, mouth-arms. 



In the Rhizostomse a vestibule is formed below the true stomach, and 

 divided from it more or less completely. Only four columns, through each of 

 which a canal passes, connect the vestibule stomach with the stomach proper 



* /S'/c. ? lamellae. 



