30 Prof. H. A. Nicholson on the 
regards its minute structure, is quite compact, and shows no 
signs whatever either of being penetrated by a system of 
tubuli or of being formed by the fusion of ectodermal spicules.” 
(2) Secondly, I was not able to recognize in Tubipora any 
thing which appeared to me to be truly of the nature of 
“tabule;’ nor did [ regard the “ axial tube” of Tubipora 
as truly homologous with the funnel-shaped tabule of Syrin- 
gopora. 
(3) I pointed out that the corallites in Syringopora are 
provided with a well-developed system of septal spines, which 
are extremely similar to the septal spines of various species of 
Favosites and Porites, whereas I had been unable to detect 
similar septal spines in the corallites of Tubipora. 
Recently an elaborate paper has been published by Mr. 
Sydney J. Hickson “On the Structure and Relations of 
Tubipora” (Quart. Journ. Micr. Sci., Oct. 1883). In this 
memoir Mr. Hickson comes to the conclusion that the genus 
Tubipora is, after all, closely allied to Syringopora, and that 
the latter is really an Alcyonarian, the Favositide also being 
referable to the Alcyonaria. In formulating this conclusion, 
Mr. Hickson passes in review the three points mentioned above 
which had led me to believe that Syringopora and Tubipora 
were not really related to one another; and I should wish, 
therefore, to make one or two remarks on each of these points. 
In the first place, as to the wide difference in the minute 
structure of the corallum in these two genera, Mr. Hickson 
remarks that “it is difficult to see why this difference should 
be considered of any great morphological importance. The 
size of the pores or ‘ tubuli,’ as Prof. Nicholson calls them, 
varies considerably in the different regions of the corallite, 
being at the younger ends much larger than they are at the 
older ends, so that it is evident that as the corallite grows 
older the tubuli have a tendency to be filled up, and a still 
further continuation of this process would make the wall of 
the corallite quite aporous. I have no evidence to prove that 
the complete filling-up of these perforations in the walls ever 
does occur in Zubipora; but should an example be found in 
which this has occurred, I should certainly not consider it 
sufficient reason for the formation of a new genus or even a 
new species. ‘That the skeleton of Syringopora ‘ shows no 
signs of being formed by the fusion of ectodermal spicules’ 
is not to be wondered at, as we possess no means of studyin 
either the development or the growth of the skeleton of this 
form, since the delicate growing ends would be broken down 
and destroyed ; and even in recent genera (such as Corallium, 
Lacaze-Duthiers), in which the skeleton is known by an 
