500 GILBERT 0. BOURNE. 



wic sich aus ilirer Lage ergibt, atis Ausscheidungen der Ekto- 

 dermzellen hervorgehen.'^ 



• After the discovery made almost simultaneously by von 

 Heider and von Koch of the calicoblast layer, these cells were 

 recognised by several other authors working on the same 

 subject. In 1886 Fowler (7) described and gave somewhat 

 diagrammatic figures of the calicoblasts of Flabellum pata- 

 gonichum, and in the same year von Heider (12) published a 

 careful memoir on the anatomy and histology of Astroides 

 calycularis and Dendrophyllia ramea. The calicoblasts 

 of the former species were not described, but special attention 

 was paid to them in Dendrophyllia. Von Heider describes the 

 calicoblasts in this species as being in many places incon- 

 spicuous, in some quite invisible, but easily discoverable in 

 others. Where they occur they are of two kinds : the most 

 numerous are polygonal or fusiform cells, one or two layers deep, 

 with a well-defined nucleus and granular contents. In other 

 places, and especially where the mesoderm of the body-wall 

 turns inwards to form the mesenteries, von Heider found cells of 

 more or less wedge shape, their pointed ends turned towards the 

 raesogloea. He says that usually these cells have no nucleus, 

 and that their inner ends are filled with exceedingly fine stria- 

 tions. Some cells adjoining these had less conspicuous stria- 

 tions, more granular contents, and a well-defined nucleus, and 

 these he regarded as being transitional between the first and 

 second kind of calicoblast. Finally, he concluded that the 

 strise were spicules of calcium carbonate formed within the cell 

 much as are the spicules of Alcyonaria. Von Heider does not 

 say whether lie examined his hypothetical spicules with a 

 polariscope. 



In the same yearW. L. Sclater (26), in a paper on Stepha- 

 notrochus Mo si ey anus, desciibed a tissue or series of cells 

 as occurring everywhere between the corallum and the meso- 

 derm. These, he says, are very different from the calicoblasts 

 figured by von Koch, being of irregular shape, separated from 

 one another by intervals so as to seldom form a definite layer, 

 and striated in an extraordinary way. Sclater^s figures leave 



