Structure of Heteropora neozelanica, Busk 



333 



figure (fig. 1, D) shows the mouths of the interstitial 

 tubes or cancelli, as well as some of those belonging to the 

 proper zocecia, to be closed by a thin calcareous pellicle, 

 which is left after incineration, and which exhibits the pecu- 

 liarity that it is perforated with numerous minute apertures 

 opposite to the mouth of each of the interstitial tubes. The 



Pier. 1. 



A. A fragment of the polyzoary of Heteropora neozelanica, Busk, of the 

 natural size (original). B. A portion of the surface of the same, appa- 

 rently somewhat altered by maceration in sea-water, greatly magnified 

 (origiual). C. A portion of the surface of the same (copied from Busk), 

 apparently in a more nearly natural state, greatly magnified. Both B and 

 C show the apertures of the zocecia and cancelli. U. Portion of the surface 

 of II pellicu/ata, Waters (copied from Waters), enlarged 25 times, and 

 showing the zocecia and cancelli. In the upper part of the figure the 

 cancelli (and the zocecia partially) are closed by a calcareous pellicle, 

 which is wanting- on the right-hand side of the figure. 



right-hand portion of the same figure shows the character of 

 the surface, where the pellicle just alluded to has been re- 

 moved. There can be no question that the existence of such 

 a calcareous (or more usually chitinous) surface-pellicle, 

 closing the cell-mouths, is a feature which speaks strongly for 

 Polyzoan affinities ; but it should not be entirely lost sight 

 of that very similar structures occur in certain extinct types 



