108 ANIMAL PHYSIOLOGY. [LESSON 31 . 



eight branches there are fimbriated (fringed) membranous extensions 

 (181, /, 182, /, &), the numerous vessels of which also anastomose 

 with the principal ascending trunk of each peduncle. On making 

 a vertical section of this Rhizostoma, thus injected, through the 

 centre of the disc (182), the internal canals (5, c) are seen, commencing 

 from the orifices of the branches (a), receiving all the lateral absorbent 

 canals (/, k) in their course, and uniting above to form one large 

 03sophageal passage (m) before entering the central gastric cavity (d). 

 The peduncles divide and subdivide like the roots of a plant; the 

 cesophageal canals follow these ramifications, and ultimately termi- 

 nate in numerous pores (/), upon the margins of the branches and 

 clavate (clubbed) ends of the ramified peduncles. These pores are 

 the commencement of the nutritive system ; they are analogous to 

 the numerous polype-mouths of the compound coral animal. 



Minute animalcules, or the juices of a decomposing larger ani- 

 mal, are absorbed by these pores, and conveyed by the successively 

 uniting oesophageal canal to the stomach. 



The nutrient fluid passes by vessels which radiate from that 

 cavity, to a beautiful network (182, h, h) of large capillaries, which 

 spread upon the under surface of the margin of the disc. Thin 

 membranous partitions (182, Z, Z) separate the cavity of the stomach 

 (d) from the four ovarial sacs, which open externally by distinct 

 apertures (i, i). 



526. In some of the higher Medusae, as in Cetonia aurita (hav- 

 ing lobes like the e,ar), the mouth is single, and opens directly from 

 the centre of the lower surface of the mantle, into a capacious sto- 

 mach, from which numerous vessels radiate to a circular canal sur- 

 rounding the margin of the disc. The mouth of Cetonia is of quad- 

 rangular form, supported by four curved cartilaginous plates, from 

 which are suspended four elongated, tapering lips, or tentacula (Figs. 

 183 and 184, a, a). On inverting the disc (184) the short, four- 

 sided oesophagus is seen in the centre, leading to a capacious gastric 

 cavity, partially divided into four sacs (183 and 184, c, c), and from 

 each of these sacs numerous alimentary canals (183 and 184, 5, b) 

 radiate towards the margin of the mantle, ramifying with great regu- 

 larity, but presenting few anastomoses compared with those of the 

 Rhizostomes. 



Around the lower part of the stomach the four ovarial sacs (184, 

 c) are placed, containing the colored ovaries, and opening externally, 

 each by a distinct aperture. From around the margin of the stomach, 

 sixteen canals come off, alternately simple and ramified, which end ID 



