Prolotheca of the Madreporaria. 21 



of perisarcal formation referred to abovCj which will be de- 

 scribed in detail in the next section. We shall have there- 

 fore to postpone the further discussion of this point for a few- 

 pages, contenting ourselves with stating that a comparison of 

 the protothecal specialization of CyathopkyUum with that of 

 Moseleya shows them to have been well nigh as wide apart as 

 they could possibly be. 



One word before leaving these early flatten ings of the 

 prototheca as methods adopted by the early Madreporaria for 

 tlie purpose of retaining the upright position. It is difficult 

 to see how, as single corals, they would be efficient for the 

 purpose unless the rims managed to touch the ground and 

 re-cement a part of the animal to the solid substratum, and 

 this, judgitjg from some of the shapes assumed, does not 

 appear to have taken place. But what is wanted is a closer 

 study of the protothecse and their earliest modifications. One 

 advantage of early flattening out they would obtain, however; 

 they would grow more slowly in height, and the leverage 

 would not be so great. Further, if this flattening out meant 

 ever so small an increase in the size of tiie base of the proto- 

 theca, we can see that it might be of some value to the 

 coral, even though the rims did not again touch the ground. 



The moment these flat-calicled forms begin to bud and 

 form colonies the advantages of the flattening become obvious, 

 as will be seen in another section. 



IV. The Perisarc. — One of the simplest of tlie really 

 important metiiods of keeping the prototheca u])right was for 

 the soft parts to bag over all round the cup until they touched 

 the ground, so as to form a secondary fleshy foot. This 

 process differs from that shown in diagram fig. 13 ^, for it in- 

 volves no gradual bending over of the rim of the prototheca. 

 1 assume that the polyp simply overflowed the edge of the cup, 

 that it reached the ground, and even expanded somewhat over 

 the substratum all round tlie point of attachment of the 

 skeleton. Bince the under surface of this overhanging flesh 

 is a continuation of that which secreted the prototheca, it 

 might be expected not only to secrete a layer over tlie outer 

 face of the cup, but also to deposit a continuation of that layer 

 where it touches the ground. This latter might be thickened 

 to form a solid pedestal, in which the tip of the prototheca 

 would be firmly flxed. Tlie fleshy foot secondarily formed in 

 the way described may have taken almost any shape, even 

 sending out radial prolongations or embracing the round 

 stems of weeds, in which cases the solid pedestals which it 

 secretes would encircle such stems, fixing the corals firmly. 



AVhen once fixed the coral may continue to grow in heiglit 



