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Show 1886.] MADREPORARIAN CORAL. 135 that all the hard parts of the coral are laid down by these cells, which can be always found between the mesodermal lamella and the hard parts. Koch (9) showed that the calycoblasts were really the remains of the basal ectoderm-cells of the embryo, so that the whole of the corallum is laid down by ectoderm, and is really, morphologically, outside the coral. This of course corrects the old view which regarded the basal ectoderm of a coral as having disappeared from the outside of the corallum, since what remains of the basal ectoderm is really within the corallum, and is the very means of forming the corallum. Koch (9, plate xx. fig. 9) gives a representation of three calycoblastic cells, which seem to be merely ordinary high epithelial cells, nucleated and filled with granules. I have found everywhere between the corallum and the mesoderm lamella a tissue or series of cells, represented in Plate XIV. figs. 10-13, cal. ; these I believe to be the calycoblasts described by Heider and Koch. That these cells must be calycoblasts is, I think, evident from their position, since they are everywhere found between the corallum and the mesoderm lamella. But in form they are very different from the calycoblasts figured by Koch, for, whereas Koch's calycoblasts are, as was said above, ordinary granulated epidermic cells, the cells which I have found in Stephanotrochus are not quadrangular but of irregular shape, and separated from one another by intervals, so that they seldom form a definite layer ; also they are striated in a most extraordinary way, as is shown in figure 12. Whether these cells are the calycoblasts of Koch I cannot with certainty say; it may be that the difference of appearance is due to the fact that Koch's figure represents these cells in a very young state, when they are doubtless more active than in the adult coral; or, again, the calycoblasts of Koch's form Asteroides may differ essentially from those of Stephanotrochus. The fact is, however, that until more is known of the anatomy of other corals, it is impossible to decide on the nature of these cells. In conclusion I must thank Prof. Moseley for kindly allowing me to examine this coral, also for his advice and assistance; so, too, I must record m y obligations to Prof. Ray Lankester, and my friend Mr. Fowler, for much help. I append a list of the principal publications referred to; I have abstained from quoting the views and discoveries of the last few years with regard to Madreporarian corals, since a very complete history of recent researches on the subject will be found in Mr. Fowler's paper (4). VI. List of Publications on the subject. 1. MOSELEY, H. N. Report on certain Hydroid, Alcyonarian, and Madreporarian Corals, procured during the voyage of H.M.S. 'Challenger.'-Report of the Voyage of H.M.S. 'Challenger,' Zoology, vol. ii. 1881. (Description of Stephanotrochus, p. 151.) 2. T I Z A R D and M U R R A Y . Exploration of the Faroe Channel during the summer of 1880 in H.M's hired ship 'Knight Errant.'- Proc. Royal Soc. Edinburgh, no. 111, p. 638. 3. M A R T I N D U N C A N , P. A Revision of the Families and Genera of |