228 THE VOYAGE OF H.M.S. CHALLENGER. 



The dark linear bodies represented as embedded in the calcareous matter 

 are cavities bored by parasitic vegetable organisms, the black clots being 

 spore-cavities. In one of the dactylopores a branched mycelial thread is seen 

 to cross over between the tubular cavities bored in the ccenosteum. 

 Fig. 7. Shows the appearance presented under transmitted light by a thin horizontal 

 section of the ccenosteum of a species of Millepora from Samboangan, 

 Philippines, in which the pores and canal-systems have become filled with 

 opaque matter. The black streaks thus shown represent the ramifica- 

 tions of the canals of the ccenosarc within the tortuous canals in the 

 substance of the ccenosteum, and show their anastomoses with the pore 

 cavities. 

 Fig. 8. Portion of a fine section of the ccenosteum, as seen under Hartnach's objective 

 No. 8, eyepiece No. 3. 



The canals bored by the parasitic fungus are seen traversing the calcareous 

 matter. 



At (a) the fibro-crystalline elements of the hard tissue project in a series 

 of points. 



PLATE XIV. 



Various structures occurring in Millepora nodosa. 



Fig. 1. View of a group of zooids in the expanded condition. In the centre is the 

 short gastrozooid, provided with only four tentacles. Grouped around are 

 seen five dactylozooids. A sixth dactylozooid belonging to the group is 

 omitted from the drawing for the sake of clearness. 

 Fig. 2. Vertical section of the decalcified living superficial lamina. A gastrozooid 

 and a dactylozooid are shown in the retracted condition. In the gastro- 

 zooid one tentacle is omitted for the sake of clearness. The open spaces in 

 the network of the ccenosarc are in the recent condition occupied by the 

 calcareous network. The vessels are in places cut through, and have the 

 pigmented endodermal cells exposed to view. 



E. Superficial layer of the ectoderm. 



D Z. Dactylozooid. 



G S. Gastrozooid. 



A. One of the spaces occupied by calcareous matter in the recent con- 



dition. 



B. Secondary branch of one of the canals of the ccenosarc. 

 0. One of the cut openings into one of the vessels. 



