CALCAREOUS SKELETON OF THE ANTHOZOA. 503 



several corals with the figures given by von Heider left no 

 doubt that the isolated skeletal element was a cal- 

 cified calicoblast cell. . . . We may look upon the super- 

 ficial layers of the slscletal elements, and of incompletely 

 calcified calicoblasts, as the outer layers of a many-layered 

 ectoderm. The ectoderm of the Madreporarian polyp" (I 

 presume Mrs. Gordon here means the calicoblast layer) "is 

 figured by Koch, Fowler, and Bourne as a simple layer of cells. 

 I have observed, on the contrary, that a section through soft 

 and hard parts shows an ectoderm, sometimes composed of a 

 simple cell layer, sometimes several cells deep. Heider's 

 figures indicate a similar observation. The calicoblasts re- 

 main adherent to one another in dense groups, or may be 

 uniformly distributed. And in this manner they are gradu- 

 ally left behind on the skeleton and completely calcify, while 

 active c(41 division develops constantly new ectodermal cells. 

 The calicoblasts adherent to the skeleton represent such as 

 were already in the course of losing living continuity with the 

 polypj at the time when the polyp was removed from the 

 skeleton. The above observations made on the skeletal sur- 

 faces will be seen to carry out fully the opinion of Heider, 

 that the skeletal deposit forms, in the first place, within the 

 calicoblast. I pointed out in the introduction that Koch's 

 view of the extra-cellular deposition of the skeleton had been 

 accepted by Fowler and Bourne. The figures given by the 

 two last-named authorities are confined entirely to prepara- 

 tions made from completely decalcified specimens. My obser- 

 vations have been made partly on dry skeletons_, partly on 

 skeletons from which the soft parts have been freshly removed, 

 organic tissues remaining here and there adherent, and partly 

 on preparations showing the body-wall in positiou.^^ 



Accompanying this statement are figures of individual scales 

 taken from the dissepiments of Galaxea, which Mrs. Gordon 

 claims to represent calicoblasts in various stages of calcifica- 

 tion. The scales as figured show a distinct striation, due to 

 their being composed of a tuft of elongate radiating calcareous 

 crystals, and several of them exhibit some dark blotches which 



