134 THE ANATOMY OF INVERTEBEATED ANIMALS. 



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Fro. 28.— I. and II.— Cyanoea capillata (after Van Beneden^). 



I. Two Hydrce tubce (Scyphistoma stage), exhibiting their ordinary character?, and 

 between them two (a, b) which are undergoing fission (Sii^obila ?tage). 



n. The two StrobUm, a and ft, three day? later. In a. tentacles are developed be- 

 neath the lowest of the Ephyrae, from the stalk of the Strobila, which will persist 

 as a Hydra tuba. 



III. Hair the disk of an Ephyra of Aurelia aurita, seen from the oral face. The 

 Bmall tentacles which lie between the mouth and the band of circular muscular 

 fibres are inside the somatic cavity, whence sixteen short and wide radial canala 

 extend to the periphery, where they are united by transverse branches. Eight 

 of the radial canals enter the corresponding lobes, and finally divide into three 

 branches: one which enters the peduncle of the lithocyst. and two lateral caeca. 

 Radiating bands of muscular fibres accompany these canals. 



rV". Side view of one of the lithocysts with its peduncle. The arrow indicates the 

 direction in which the cilia of the exterior work. 



' "Eecherches sur la Faune littorale de Belgique. Polypes." 1866. 



