248 G. HERBERT FOWLER. 



embryo is attached. Where septa are to be formed the three body 

 layers, endoderm, mesoderm-lamella, and basal ectoderm, rise upwards 

 as a fold into the coelenteron ; and as they rise, coral is deposited 

 beneath them which fuses with the original disc ; the septa are thus 

 also deposited outside the basal ectoderm. Then they begin to 

 bifurcate at their distal ends. The originally basal ectoderm to 

 which the secretion of the skeleton is attributable persists in the adult 

 as the calycoblasts of v. Heider. 



Von Koch further asserts that the theca results from the fusion of 

 the bifurcating ends of the septa ; but, though not venturing to deny 

 this, I would point out that he neither describes the process nor gives 

 figures to illustrate it; whereas, on the other hand, we have the direct 

 evidence of L. Duthiers to the effect that the theca and septa arise 

 independently of each other ("les septa et la muraille ne sont pas 

 unis"), and a figure, which appears to bear out his statement. It must, 

 however, be borne in mind that Lacaze Duthiers may have described 

 as theca what v. Koch terms epitheca, a secretion of the lower portion 

 of the lateral endoderm of the embryo which fuses with the periphery 

 of the original basal disc, and ultimately combines also with what he 

 terms the true theca, formed as above mentioned, to become the outer 

 wall of the corallum. Were this the case, however, the costse could 

 not be, as he regards them, the peripheral ends of the septa. But the 

 question can only be finally settled by a study of the embryonic 

 development of widely different forms. 



Professor Moseley has published a preliminary note on Seriato- 

 pora and Pocillopora (10). These forms were originally classed with the 

 Tabulata, but his account of their anatomy brings them into close 

 connection with the other Madreporaria at present described. The 

 polyps of Seriatopora are oval in outline, with twelve short tentacles, 

 which in complete retraction are covered over by the indrawn margins 

 of the disc, a condition common in Actiniaria, but very rare in 

 Madreporaria. There are twelve mesenteries, only two of which, 

 the same two in every polyp, are enormously long and bear 

 mesenterial filaments and generative organs. The elongation of 

 this pair of mesenteries deep into the colony suggests an inevitable 

 comparison with the Alcyonaria ; and the similarity is strengthened 

 by the marked orientation of the polyp, for a division into " dorsal" 

 and "ventral" halves is clearly distinguishable in both soft 

 tissues and corallum. Two of the septa are very rudimentary, and 



