234 WILSON. [Vor. II. 
which are entoccelic, extend as high and higher than Fig. 41. 
Further, in Fig. 42 it is evident that twelve tertiary septa have 
started to develop, though only a few of them extend an appre- 
ciable distance above the theca. As only twelve pairs of mes- 
enteries have been formed, the tertiary septa are temporarily 
exoceelic. Transverse and longitudinal sections through such a 
polyp as this show very clearly that the growth of the theca is 
continuous and from below upwards. Nowhere are two septa 
found which actually pierce a mesentery to form the theca, but 
everywhere the growing theca pushes the tissues of the mesen- 
teries upwards. Where the theca is formed in such a manner 
as this, it is out of the question to believe, after Von Koch, that 
the radial cracks found in ground sections of the theca are due 
to the existence in these radii of the atrophied remains of the 
lower portions of the mesenteries. 
The costz in Figs. 41 and 42 are very feebly and irregularly 
developed. Each septum has, however, three or four teeth 
along its outer edge, and also a few on its inner edge. All the 
teeth on the outer edge of the septa open directly to the exte- 
rior over the side wall of the coral. In Fig. 41 the septum in- 
cluded between the near pair of directive mesenteries is cut 
just below the point at which it thus opens. Fig. 40 givesa 
more highly magnified view of the same septum cut at the level 
of its opening. In Fig. 42 a tooth has opened at mm, and another 
at z is sectioned just beyond its opening. The apertures are 
of good size, and through them the external ectoderm is contin- 
uous with the calycoblast layer. This peculiarity of the teeth 
is no longer found in JZanzcina after asexual multiplication has 
begun, and only a few teeth open to the exterior in single polyps 
with the full complement of septa. In one such polyp, however, 
all the teeth opened in this way. From this it would seem that 
the connection of the calycoblast layer with the surface ecto- 
derm at these points is a characteristic of youth which is gradu- 
ally lost. It is possible that this peculiarity may have been ac- 
quired in order to bind the little polyp and its simple skeleton 
firmly together. 
X. ORIGIN OF THE ANTHOZOA. 
As is well known, the reigning view as to the origin of the 
Anthozoa is that advanced by Claus and Haeckel, according to 
