THE ANATOMY OF THE MADREPORARIA. 
583 
which fuses with the original disc ; the septa are thus also 
deposited outside the basal ectoderm. They then 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. 
Yon 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 ulti- 
mately 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 costae could not be, as he 
l’egards 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 ( 10 ) has published a preliminary note on 
Seriatopora and Pocillopora. 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 out- 
line, 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 mesen- 
teries 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” 
