302 GILBERT 0. BOURNE. 



method invented by G. von Koch^ to study the relations of the 

 hard and soft parts in situ. This method, which is described 

 in the ' Proceedings of the Zoological Society/ 1880, p. 41, 

 yields valuable results with smaller corals, but requires con- 

 siderable experience, and is not wholly satisfactory when so 

 large a coral as Fungia is dealt with. 



Von Koch, in a short note on the anatomy of Fungia and 

 other Madreporaria, published in the beginning of this year, 

 rightly says that its structure is essentially the same as that of 

 other Madreporaria, but he makes no mention of the peculi- 

 arities which obtain from the relation of the soft parts to the 

 synapticula, and his diagram is incorrect in some particulars 

 (23). 



The Mesenteries. — It is obvious that, since the lower 

 parts of the interseptal loculi are broken up by synapticula, 

 there must be some corresponding modification of structure in 

 the mesenteries, if the latter structures are present in Fungia. 

 Professor Duncan was so much struck with this in his studies 

 on the corallum that he was led to express a doubt whether 

 mesenteries could exist at all (5). Transverse sections show 

 that mesenteries do exist, and that in all their essential charac- 

 ters they have the arrangement typical of Hexactinian 

 Actinaria. They are arranged in pairs, each pair being dis- 

 tinguished by the arrangement of its longitudinal muscle-fibres, 

 which are placed on the adjacent faces of the two mesenteries 

 composing the pair, except in the case of the two pairs of 

 directive mesenteries, one pair at each end of the long axis of 

 the mouth, in which the longitudinal muscle-fibres are placed 

 on the reverse sides. The space included between each pair 

 of mesenteries is an entocoele (Fowler, 9) and in each entoccele 

 there is a septum. There are seven orders of mesenteries in 

 the Fungia which I am describing, corresponding to the 

 seven orders of septa. 



The primary and secondary mesenteries are attached to the 

 stomodseum, and in their upper parts traverse the whole space 

 from the mouth to the periphery of the disc. The tertiaries 

 are not attached to the stomodseum, but reach nearly to it. 



