BED OB PBECIOUS COBAL. 11 



The fleshy external part (ccenenchyma), in which the polyps 

 are placed, is canaliferous, has spicules, which are, according to 

 Ridley, of one type, "viz. a hexahedral oblong form, the angles 

 being formed by broad truncate but microtuberculate tubercles 

 which preserve the chief features of their characteristic form 

 throughout all varieties of the external form of the coral."* It 

 surrounds the dense, inflexible, calcareous axial part (the coral 

 of commerce), which consists of fused spicules formed by the 

 fleshy part, and it is stated to be devoid of an investing cellular 

 (epithelial) layer, whereas Gorgonia and its immediate allies 

 have the latter, the central rod in these being ectodermal. 

 Cavolini compared the fleshy and the hard parts to periosteum 

 and bone — a somewhat crude simile — while Boccone thought 

 the hard axis was only formed by juxtaposition. 



The vessels ramify through the whole of the fleshy part, the 

 larger parallel ones next the hard axis, the smaller forming a 

 reticulation throughout the entire layer. They carry a nutritive 

 fluid originating in the chyne in the interior of the polyps, as 

 clearly described by Peyssonnel. It is the so-called " milk " of 

 coral. The fleshy part is translucent when distended by water, 

 is cellular, and has the calcareous spicules already mentioned. 

 Externally is the cellular ectoderm, which by fusion of its cells 

 appears as a structureless layer. The fleshy part has a tendency 

 to produce buds everywhere, even injuries being followed not 

 only by repair but by branching. 



The sexes of the red coral are generally borne on separate 

 colonies ; rarely both occur on the same branch. No external 

 distinction exists between them, except that in dead branches 

 the eggs become yellow, whereas the products of the males 

 remain milky. Both elements are produced in the sarcosome in 

 the deeper parts of the polyps, as in Alcyonium. The eggs are 

 developed internally, and the larva escapes by the mouth (as a 

 planula) from May to September, and occasionally as late as 

 December. A close-time, therefore, could only be carried out by 

 the division of the entire coral-bearing area into sections. The 

 larva swims freely in the water, and becomes pear-shaped before 

 fixation, sinks to the bottom, fixes itself to stone or rock, and 

 becomes flattened. 



* Proc. Zool. Soc. 1882, p. 223. 



