58 ZOOLOGY. 



ramifications. The whole canal system is connected to- 

 gether by a freely anastomosing mesh- work of smaller ves- 

 sels, and communicates freely by numerous offsets with the 

 cavities of the calicles." As the animals increase in num- 

 bers and die, the coral stock increases in size, the layer con- 

 taining the living animals forming a thin film only, the 

 bottom of the little cups or pores forming a table or plat- 

 form, whence the term Ttibulata, originally applied to this 

 group, the old calicles being divided by a series of trans- 

 verse plates or laminge, separating them into series of cham- 

 bers. Moseley shows that the corallum of Millepora is dis- 

 tinguished from all other coralla by its systems of canals 

 branching in an arborescent manner, while the tabulate 

 structure occurs in certain Alcyonaria, Zoantharia, and in 

 other Hydroida ; hence the group Tabulata, as previously 

 stated by Verrill, is an artificial one. 



The animals of the Millepora are of two kinds ; those in- 

 habiting the central cup or pore are short, thick zooids, 

 with a mouth and four tentacles, and only half a milli- 

 metre in height ; those in the smaller pores are longer and 

 slenderer, about one and a half millimetres in height, with 

 from usually five to twenty tentacles, situated at irregular in- 

 tervals from the base to the summit of the body. The body 

 cavities of the zooids end in blind sacs at the bottom of the 

 cup, but are continuous beyond with the canals of the hy- 

 drophyton, the latter being defined by Allman as forming 

 in the Hydroids " the common basis by which the several 

 zooids of the colony are kept in union with one another." 

 As we know nothing of the mode of reproduction of Mille- 

 pora, we must leave it for the present near Hydractmia, to 

 which the adult animals are nearest related. Moseley also 

 discovered that Stylaster, a beautiful pink coral which grows 

 at Tahiti, with the Millepora, is in reality a Hydroid, and 

 not a true coral polyp, as has always been supposed. That, 

 finally, Millepora is a true Hydroid is proved, Moseley thinks, 

 by the peculiar structure of the hydrophyton, the forms of 

 the zooids, the absence of all trace of mesenteries, the ap- 

 parent septa present in the tentacles, and by the presence 

 of thread-cells of the form peculiar to the Hydrozua. The 



