258 COELENTERATA HYDROZOA chap. 



vertical tube divided into sections by horizontal calcareous plates 

 (Fig. 129, Tah). These plates are the "tabulae," and constitute 

 the character upon which Millepora was formerly placed in the 

 now discarded group of Tabulate corals. 



The coral skeleton is also perforated by a very fine reticulum 

 of canals, by which the pore-tubes are brought into communica- 



FiG. 128. — A portion of a dried colony oi Millepora, showing the larger pores (gastro- 

 pores) surroiin<led by cycles of smaller pores (dactylopores). At the edges the 

 cycles are not well defined. 



tion with one another. In the axis of the larger branches and 

 in the centre of the larger plates a considerable quantity of the 

 skeleton is of an irregular spongy character, caused by the 

 disintegrating influence of a boring filamentous Alga.^ 



The discovery that Millepora belongs to the Hydrozoa was 

 made by Agassiz ^ in 1859, but Moseley^ was the first to give 



^ This organism is usually described as a fungus (Achlya), but it is probably a 

 green Alga. See J. E. Duerden, Btill. Aincr. 3Ius. Nat. Hist. xvi. 1902, p. 323. 

 '^ Bihl. Univ. de Geneve, Arch, des Sciences, v. 1859, p. 80. 

 =* Phil. Trans, cxlvii. 1876, p. 117. 



