226 Proceedings of the Boyal Society 
or markedly fibrous sclerencliyma (fig. 3, a and b). When this is 
the case, the outer layer is usually of a conspicuously lighter colour 
than the internal layer, and this gives rise to certain phenomena 
which deserve a moment’s notice. When, namely, these two 
layers exist, the septal spines (fig. 3, b) always take their origin 
from the outer light-coloured layer, and penetrate through the 
inner laminated and dark layer on their way to the visceral 
chamber. Hence, in longitudinal sections which divide the ivcdl 
of the corallites (fig. 3, c), we observe vertical rows of small 
rounded spaces, which have a lighter colour than the surrounding 
tissues. These light circular spaces might easily be mistaken for 
pores in the wall, or for transverse sections of canals running in the 
wall ; but they are really the cut ends of the spiniform septa 
divided near their bases. 
5. Supposed relationships between Tubipora, and Syringopora . — 
Owing to the marked external resemblance which subsists between 
the corallum of Tubipora and that of Syringopora , it has been 
commonly held by naturalists that the two genera are nearly related, 
and that the latter genus is, therefore, referable to the Aleyonaria. 
Amongst the later authorities who have adopted this view may be 
mentioned Zittel (“Handbuch der Pakeontologie,” vol. i. p. 211) 
and Moseley ( a Voyage of H.M.S. Challenger,” vol. ii. p. 125). My 
own view, on the other hand, has been that there is no real affinity 
between Tubipora and Syringopora , and that the latter is really 
referable to the Zoantharia perforata , and allied to the Favositidse 
(“ Pakeozic Tabulate Corals,” p. 213). In considering this question 
with a view to arriving at some decided conclusion, it may be as 
well to summarise the chief points of likeness and unlikeness 
between Tubipora and Syringopora. The points of resemblance 
between the two genera are as follows : — 
(a.) It must be admitted, in the first place, that there exists a 
very remarkable general likeness of the corallum of Tubipora to that 
of Syringopora. In both, namely, the corallum consists of slightly 
separate cylindrical corallites, of comparatively great length, bound 
together by horizontal processes or floors. 
( b .) A still more striking point of likeness, as of a really much 
more fundamental character, is to be found in the fact that in both 
genera the visceral chambers of the polypes are placed in direct 
