THE ANATOMY OF THE MADEEPORARIA. 13 



those which here are well developed are, in the Madreporse 

 mentioned above, rudimentary, and vice versjl. 



iv. Memoirs referring to the Genus : 



Milne-Edwards and Haime, ' Hist. Nat. Corall./ iii, p. 

 311, pi. f4, fig. 3. 



Klunzinger, ( Korallthiere des Rothen Meeres/ ii, 69, pis. 

 vii, viii. 



Agassiz, ' Nat. Hist. United States/ iv, p. 296, pi. 15, 

 fig. 15. 



POCILLOPORA BREVICORNIS (figS. 14, 15). 



The anatomy of this species agrees so closely with that of 

 Seriatopora subulata that only points of difference between 

 the two need be quoted. 



The corallum is, of course, different in its mode of growth, 

 as upon this the distinction between the two genera is based, 

 but this difference does not affect the anatomical relations of 

 the polyps. The method of support of the external body wall 

 is identical with that in Seriatopora ; the tentacles agree in 

 the two forms, though, as they are fairly well expanded in my 

 specimens, it does not appear whether they are capable of in- 

 troversion or not; the stomatodseum is less distinctly conical 

 than in the cognate genus. 



As regards the mesenteries, the. only points of difference 

 noticeable are, that in Pocillopora those denoted in the dia- 

 gram (fig. 9) by the numbers 3, 10, are not proportionately so 

 much longer than those marked 1, 5, 8, 12, and that a mesen- 

 terial filament may sometimes be detected on the four last 

 mentioned; in other words, the tendency observed in both 

 Seriatopora and Madr. Durvillei towards the exclu- 

 sive assumption of function on the part of six mesen- 

 teries and towards a correlated retrogression (?) on 

 the part of the other six, has not attained to such a 

 pitch in Pocillop. (and Madr. aspera) as in the other 

 two forms. 



The statement of Professor Moseley (10), that " the mesen- 

 terial filaments are not enclosed in prolongations of the 



