WITHIN TIIK GENUS OENBRONEPIITJlYA. 39 



§ 6. If, as I think probable, the Glouievates, Divaricates, and 

 Umbellates represent three distinct stocks or lines of evolution, 

 the particular problem is to discover whether similar morpho- 

 logical radiations can be discerned in each of these main 

 divisions. A prior question is — What characters can be re- 

 garded as having real morphological importance? 



1. Negatively, it is quite plain that little emphasis can be laid 

 on the size of the colony, looseness or density of branching, 

 amount of sterile stalk or colour. 



2. Positively, the features which seem most indicative of 

 relationship are in order of importance : — 



(1) the architecture of the anthocodial armature — e.^., whether 



crown and points are distinct, the number of spicules in 

 each point, their degree of projection and their difierenti- 

 ation within the point ; 



(2) the difierentiation of the supporting bundle ; 



(3) whether the polyps are marked by long stalks or are very 



short-stalked ; 

 (4). characteristic features in the spiculation, such as the occur- 

 rence of particular forms in special regions of the colony — 

 e. g,, the " sterile stalk," canal-walls. 



§ 7. In studying the possible relationships of different species, 

 I make the following provisional assumptions : — 



(a) That the presence of very numerous small spicules in the 

 anthocodial points is more primitive than a reduced number 

 of large spicules. 



(/;) That the absence of a definite " crown " is more primitive 

 than its difierentiation. 



(c) That a slightly differentiated supporting bundle with a 

 large number of spindles tending to form a sheath rather than 

 a buttress is a more primitive condition than the differentiation 

 of a bundle out of a few large spicules. And here it may be 

 noticed that in a few species— e. g., JD. clavata, the supporting 

 bundle is so slight that the polyps may at first sight be mistaken 

 for those of a Eunephthya, where there is no supporting bundle 

 whatever. 



{d) That the more primitive forms show :— 



(1) less variety of spicule : i.e., are predominantly provided 

 with spindles, the characteristic spicule, and less variety 

 of spicule in the anthocodial point ; 



(2) less localization of particular forms of spicule in parti- 

 cular areas. Thus there can be no doubt that the 

 presence of special interlocking spicules in the " sterile 

 stalk " is a later differentiation ; 



(3) the presence of few spicules in the canal- wall. 



Thus D. piitteri with a multitude of canal- wall spicules is in other 

 respects highly specialized. Conversely, it is interesting that 



