24 MADREPORARIA. 



however, somewhat more complicated. For it is not one polyp budding from another, but a 

 colony, consisting of a multitude of polyps which bud simultaneously from the surface 

 of a previous multitude, and they fit so accurately over one another that each new polyp 

 continues the growth of the skeleton of its corresponding polyp of the former colony. This is 

 certainly one of the marvels of growth which not only baffles our powers of conception, but 

 demands investigation, if for no other reason, at least to ask how it fares with any inter- 

 calicinal buds. Are they repeated just at the right age and stage in the new generation ? 

 The process requires the assumption of something more than a new bud : some extensive pro- 

 cess of liistolysis would alone suffice, in which an old colony begins to die down, undergoes 

 some very extensive internal re-organisation, and starts again, an entirely new colony, which fits 

 so accurately into the skeleton of the old, that, beyond secreting a tabular floor by its own new 

 ectoderm, no break can be seen in its skeletal continuity. We once more ask whether this is 

 the real explanation of what we have always referred to as repeated withdrawal of the polyp 

 as tlie skeletal walls grow in height ; or do both processes occur consecutively, as suggested 

 above for the large fossil solitaries ? 



Here are matters of the first moment for the coral morphologist. They require investiga- 

 tion. As probably some contribution to it, I would call attention to an interesting observation 

 of Professor Duerden's,* of which he offers no explanation. He noted individual stocks, 

 especially of " P. astrmoides," of which all the polyps seemed to be in a state of maceration, 

 though others living around them were perfectly normal. They appeared to be " alive and 

 normal in colour, but upon examination with a lens no distinct polyps or tentacles were recog- 

 nisable. The whole of the soft tissues seemed to be a gelatinous mass in process of decay, the 

 coloration being due to the persistence of the yellow pigment cells characteristic of this 

 species." 



Is it not possible that this strange condition indicates some internal reconstitution of the 

 organism into fresh individuals which build symmetrically upon the old skeleton ? It is to 

 be hoped that ere long colonies, in the condition described by Professor Duerdin, will be 

 submitted to minute microscopic observation. It is apparently a kind of budding, so 

 specialised that the parent is entirely absorbed by the bud which in every respect repeats 

 the form of the parent — a process explicable only by referring it back to the more primitive 

 fission. 



It remains for us here to add that, though the discovery of this new principle of growth 

 must sooner or later make itself felt in coral systematics, no use of it has been made in the 

 systematic portion of this Volume, inasmuch as it was not discovered till the descriptions were 

 all in print. Some reference, however inadequate, is made to it in the Table III., which deals 

 comparatively with the growth-forms of the specimens here described. 



• "The coral Siderastra-a," Washington, 1904, p. 18, pubhshed 1904 by the Carnegie 

 Institution. 



