INDIAN OCEAN GONIOPOR^E. 85 



to hold that one common parent form might he able to produce all the forms displayed by the 

 genus in any particular locality, the ultimate differences, no matter how great they appear, 

 being due entirely to the start made by that parent polyp in one direction or another. The 

 nature of the start may depend upon the character of the environment in which the larva 

 becomes sessile. At the present, however, our belief in such unlimited plasticity requires 

 restraining until we understand better what heredity means. The fact that the parent form 

 repeats the generic characters reveals the presence of that force beyond question. What may, 

 however, be open to question is whether any of the derived forms are stable enough to have 

 acquired enough of this force to be able to repeat themselves indefinitely from within, and 

 independently of the environment. The evidence so far seems to be that such force of 

 heredity is acquired by the derived forms. There are specimens in the Museum showing two 

 very distinct forms of the genus Turbinaria growing side by side upon the same pearl shell. 



Group IV.— INDIAN OCEAN. 



Containing descriptions or records of Gonioporoz from Ceylon (1); Maldives (1-4); Mauritius (1); 



Seychelles (1). 



55. Goniopora Ceylon * a) l. (PI, VI. fig. 9 ; PI. XIII. fig. 5.) 



[Ramesvaram, Gulf of Manaar, coll. Thurston ; British Museum.] 



Description. — Corallum rises into columns 15 cm. high and more, with smooth, rounded, 

 very slightly bulging tops, hence only gradually thickening as they rise. The sides may be 

 rounded, or flattened, broad and wavy, 6-7 cm. thick. Free edge formation is not very con- 

 spicuous. The living layer descends some 4-5 cm. The epitheca does not form a continuous 

 pellicle, but is in wrinkled bands running round the small edges. 



The calicles are large (4-5 mm.), open, conical, and very conspicuous, with great numbers 

 of buds of all sizes in the angles. At the summit, where growth is most active, the calicles 

 are generally smaller and some 4 mm. deep ; at the sides (fig. 9) they are larger and more 

 open, and gradually diminish to 2 mm. deep or less. The wall is very thin, often incomplete, 

 hence perforate, and zigzag, though owing to the thickness of the septal lamina?, which may 

 be almost described as exsert, at first sight it may appear thick. Seen from above the septa 

 are sharply wedge-shaped, thick, and very slightly differentiated where they join the walls. 

 Most show a tendency to a spiral twist. Their edges as they descend are conspicuously and 

 regularly denticulate, the perforations usually being in vertical series. The primaries project 

 further in than the rest, and their edges become thick and coarse. The complete formula is 



* It has been pointed out to me that Madras would have been a better district name, but it 

 was too late to alter it. 



