134 THE ANATOMY OF IXYERTEBRATED AXHIALS. 



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Pig. 28— I. and IL— Cyana>a capittata (after Van Beneden 1 ). 



I. Two Hyrtrce tubce (Scyphistoma stage), exhibiting their ordinary characters, and 



between them two {a, b) which are undergoing fission (Strobila stage). 



II. The two Strobiles, a and 6, three days later. In a. tentacles are "developed be- 

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

 as a Hydra tuba. 



III. Half the disk of an EpJiyra of Aurelia aurita, seen from the oral face. The 

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

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

 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. 



IV. Side view of one of the litbocyste with its peduncle. The arrow indicates the 

 direction in which the cilia of the exterior work. 



1 " Eecherch.es but la Faune littorale de Belgique. Polypes." 1866. 



