THE VOYAGE OF H.M.S. CHALLENGEE. 



PART II.— ON HELIOPORIDJE AND THEIR ALLIES. 



Introduction, ...... 



Methods employed, ..... 



Observations on Heliopora ecernlea in the living condition, 



Structure of the coraUum of Heliopora ccerulea, 



Mode of the growth of the corallum, . 



Mode of deposition of the hard tissue, 



Blue coloration of the corallum. 



Structure of the soft tissues of Heliopora ; ectoderm, . 



Endoderm ; soft tissues of tubes and calicles, 



Canal systems, 



Xematocysts, . 



Structure of the polyps, 



Tentacles, 



Stomach ; mesenteries and muscles, 



Generative organs, 



Disposition of the dorsal and ventral aspects of the polyps, 



Structure of a species of Sarcophyton, 



Terms employed — zooids, .... 



autozooids, .... 



siphonozooids, 



sarcosome, 



vascular system, 

 Disposition of the dorsal and ventral aspects of the zooids, 

 General remarks, ..... 



Affinities of Heliopora, .... 



Characters of the family Helioporim;, 

 Tubular ccenenchym of Heliopora and its homologues, 

 Fossil allies of the Helioporid^;, 

 Alliance of Syringopora and Tubipora, 

 On the septa of Heliopora, .... 

 Zooids of Sarcophyton and Pennatulids compared, 

 Development of Alcyonarians and Zoantharians compared, 



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