Skeleton in Corallium, Tubipora, and Syringopora. 31 
examination of its growth to be composed of fused spicules, 
no evidence of them can be seen in thin transverse section 
through the hard parts.” 
With regard to Mr. Hickson’s statement that it is “ difficult 
to see’? why the difference between the spicular skeleton of 
Tubipora and the compact skeleton of Syringopora “ should 
be considered to be of any great morphological importance,” I 
can merely say that this is clearly a matter of opinion. For 
my own part I find it difficult to see why this distinction as to 
the minute structure of tle corallum should not be considered 
as of great morphological importance; and some investiga- 
tions that I have recently been carrying out have very much 
confirmed me in this opinion. The hypothesis, on the other 
hand, that possibly an aporous form of Tubzpora may be in 
future discovered, would not lead me to disregard the known 
structure of the actual form of Yubipora. Moreover it is not 
only that the skeleton of Syringopora does not show “ signs 
of being formed by the fusion of ectodermal spicules,” but that 
it does show signs of having a structure very similar to that of 
various undoubted recent Zoantharians, and quite unlike that 
of any known recent Alcyonarian. Again, it is not the case 
that ‘ we possess no means of studying either the develop- 
ment or the growth of the skeleton” of Syringopora, “ since 
the delicate growing ends would be broken down and de- 
stroyed.” On the contrary, as regards the growth of the 
skeleton, any good collection of Paleozoic corals contains 
perfect colonies of Syringopora, in which the growing extre- 
mities of the tubes are as well preserved as we have any 
ground for supposing that they would be were the coral a recent 
one; and an examination of these growing ends shows that 
they do not differ in minute structure from what is found in 
the older parts of the tubes. 
Lastly, as regards the structure of the skeleton in Corallium, 
Mr. Hickson has fallen into error, and his argument, in reality, 
points in the opposite direction. He argues, namely, as I 
understand him, that Syringopora may have really had a 
spicular skeleton, because in the recent genus Coralliwm, 
though we know from an examination of its growth that the 
skeleton is really composed of fused spicules, “ no evidence of 
them can be seen in thin transverse section through the hard 
parts.” As a matter of fact, however, such spicules were 
shown to exist in sections of the skeleton of Corallium by La- 
caze-Duthiers, and were both described and figured by Kolliker 
(‘Die Bindesubstanz der Ceelenteraten,’ p. 146, Taf. xvi. 
fig. 9). It is not necessary, however, to quote authorities on 
such a point, as I have never had any difficulty in demon- 
