336 TABULATE CORALS. 



the transversely -divided columns of Labechia connected by 

 irregular lines representing the cut edges of the lenticular 

 vesicles ; while in the Fistulipoj^a we have the cut sections of 

 the large tubes united by lines, which are also the cut edges of 

 the lenticular vesicles, but which in this case are regular in form 

 and mark off the boundaries of the small corallites. When we 

 consider the above resemblances, we are very much tempted to 

 conclude that LabecJiia is a coral similar to Fistulipor-a (or to 

 Propora in the series of the HelioporidcB), but having the vis- 

 ceral chambers of the large corallites largely or totally obliter- 

 ated in process of growth. The conversion of some of the 

 corallites into spines or columns is a phenomenon which we 

 have seen to occur in some of the MontictdiporidcE {e.g., in 

 Dekayia), and would not, therefore, be an absolutely unex- 

 ampled occurrence. If, however, we were to accept this view, 

 we should have to believe that in Labechia it is the large coral- 

 lites of the colony which have their cavities obliterated, and thus 

 become columnar, no such thing having been noticed among 

 other types of corals. Moreover, in the case of corals like 

 Fistulipora and Propora, we know exactly what is the nature 

 of the interstitial vesicular tissue. We know, namely, that this 

 tissue is formed simply by the coalescence and anastomosis 

 of the tabulse of a series of small interstitial corallites, the 

 walls of which are imperfectly developed ; and we know that 

 the calices of these small corallites can often be detected on 

 the surface in the intervals between the large tubes. (In this 

 connection it should be remembered that the mouths of the 

 small corallites of FisHilipora are commonly closed by a cal- 

 careous membrane, so that only the calices of the large tubes 

 can be recognised at the surface). On the other hand, there 

 is no distinct evidence that the vesicular tissue of Labechia 

 is formed in a manner similar to the above, by the conflu- 

 ence of the tabulse of a series of small corallites ; and, upon 

 any view, we are confronted with the inexplicable circum- 

 stance that no apertures or " calices " have ever been cer- 

 tainly detected on the surface of the skeleton. Till open- 



