172 ON THE POSTEMBRYONIC DEVELOPMENT OF CYCXOSERIS. 



Fungia by Bourne 1 , would ultimately prove to be of very wide distribution among 

 the discoid forms of the Madreporaria, I carefully collected in Rotuma and Fiji all 

 the fixed solitary reef-corals I found, upwards of fifty in number 2 . All these were 

 young Fungia with the exception of three or four, which seemed to me to be 

 referable to the genus Cycloseris. On Dr Wil ley's return he kindly handed over to 

 me two adult and twenty-four young specimens, which he had collected at low tide in 

 rock pools at the base of the cliffs in Blanche Bay, New Britain. One of the adults 

 I have referred to Cycloseris hexagonalis, while fifteen of the young specimens form 

 an almost complete series to it. Two oval anthocyathi with very distinct scars on 

 their aboral surfaces, evidently but recently detached from their anthocauli, are 

 referable to another and probably new species of Cycloseris, which I do not propose 

 to describe as it is not clear how far they have as yet attained their adult 

 characters. 



Cycloseris differs from Fungia as described by Duncan 3 mainly in the fact that 

 the theca in the former is imperforate. The septa of the species of the former, that 

 I have examined, as compared with Fungia, are not at all, or not nearly so markedly 

 ridged. The spines on their sides are arranged perfectly regularly, a line along each 

 ridge, or in lines, which diverge in a similar manner to the ridges of Fungia 4 , and 

 are not scattered irregularly over their surfaces. The theca further extends to a 

 definite distance from the ends of the septa, and is not irregularly cut into between 

 them as in Fungia. The synapticula are similar to those of Fungia, but do not 

 extend so high above the theca, nor so far outwards between the septa. They do 

 not in fact give nearly the same support to the corallum as those of Fungia. 



The earliest fixed stage of growth or instar, that I have examined, is a young 

 trophozooid 5 , 0'4 mm. in diameter by about the same in height (Fig. 10). It is attached 

 to the aboral surface of a dead anthocyathus, which also has growing on it an anthocaulus. 

 The base of the latter and the dead anthocyathus are both much overgrown by 

 incrusting Polyzoa, Foraminifera, Sponges and Worm-tubes. The young trophozooid 



1 "On the Posternbryonic Development of Fungia," Sci. Trans. Hoy. Dublin Sec, vol. v. p. 205 et seq. (1893). 

 Vide also " On the Anatomy of the Madreporarian Coral Fungia," Q. J. II. S., xxvii, p. 359, by the same author. 



- A careful examination of these specimens has shown me that they very fully confirm Bourne's account 

 so far as it applies to the gross structure of the skeletal parts in the different stages. It seems to me to 

 be probable, though, that stalked individuals may be budded off from the free anthocyathus, where conditions 

 are unfavourable for its continued growth, owing to incrusting organisms, sand, etc. These afterwards may 

 themselves become anthocauli, detaching anthocyathi. 



3 Jour. Linn. Soc. Zool., vol. xvm, pp. 141 and 149. 



4 Comp. " Microscopic and Systematic Study of Madreporarian Types of Corals." By Maria Ogilvie. Phil. 

 Trans. Boy. Soc, vol. clxxxviii, p. 83 et seq. fig. 37. 



5 I have throughout used the terms proposed by Bourne for the different instars of Fungia (loc. cit., 

 p. 206):— 



Trophozooid. The individual C'aryophyllia-like form developed directly from the ovum. 



Anthoblasts. Buds from the trophozooid. 



Anthocyathus. The discoid Fungia form, whether free or attached, developed from a trophozooid, or an 



authoblast. 

 Anthocaulus. The pedicle, which carries the anthocyathus, and after the detachment of the latter usually 



gives rise by re-growth to a new anthocyathus. 

 The term "instar" was advocated by Sharp (Carnb. Nat. Hist., vol. v, p. 155) for the successive stadia of 

 insects. It seems to me that the term may be very usefully applied here to imply simply a stage of growth. 



