76 THE GENUS MONTICULIPORA. 



in both genera the colony consists of two sets of tubes, 

 while both have their tubes crossed by transverse partitions. 

 Such transverse partitions of the tubes (or, as we may loosely 

 call them, " tabulce ") occur, however, in organisms of such 

 exceedingly diverse affinities, that we can, admittedly, attach 

 no value to the last mentioned of the above resemblances. 

 A mere similarity in general form, appearance, or mode of 

 skeletal conformation is also of no classificatory weight, since 

 we could find species of Favositcs or Pac/iypora which in 

 these respects are quite like either Moiiticulipoj-a or Hctero- 

 pora ; so that, after all, the resemblances between the two 

 genera under consideration dwindle down to a comparatively 

 small quantity. 



On the other hand, to set against the mostly superficial 

 points of resemblance above noted, we have a number of 

 fundamental structural differences. Thus, in jMontiaUipoi-a 

 the walls of the tubes are imperforate, there are no traces 

 of radiating spines or " septa," and in the dimorphic or 

 trimorphic species there are usually important structural dif- 

 ferences as regards the different groups of corallites. In 

 Hetei'opora, on the contrary, the walls of the tubes are tra- 

 versed by a very remarkable and exceptionally developed 

 canal-system, the tubes possess in their outer portions a 

 well-developed series of radiating spines arranged in vertical 

 rows (sometimes, at any rate, if not always ^), and the inter- 

 stitial tubes are in no way structurally different from the proper 

 zooecia. 



In the face of the above distinctions, I feel compelled to 

 believe, in the meanwhile, that there is no real relationship 

 at all between Heteropora and Montictdipora. This belief 

 would not, of course, constitute any valid ground for denying 



1 It is true that radiating spines have not generally been observed in Heteropora, 

 and that even in H. neozelanica, where they are plentifully developed, they seem 

 not to have been noticed by such excellent observers as Professor Busk and Mr 

 Waters. I ascribe this, however, to their very fragile nature, and to the general 

 neglect of tangential sections, in which alone they can be readily made out ; and I 

 entertain little doubt that they occur generally in the genus. 



