134 THE ANATOMY OF INVERTEBRATED ANIMALS. 



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Fro. 28.— I. and 11.— Cyancea capillata (after Van Beneden 1 ). 



I. Two Hydros, tubal (Scyphisfoma stage), exhibiting their ordinary character?, and 



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



II. The two Strobilce, a and b, three days later. In a. tentacles are developed be- 

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

 as a Hydra tuba. 



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

 Hmall tentacles which lie between the mouth and the band of ciicular 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 

 bianches: 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 lithocysts with its peduncle. The arrow indicates the 

 direction in which the cilia of the exterior work. 



1 " Recherchcs sur la Fauae littorale de Belgique. Polypes." 1866. 



