THE MEDUSA OF MILLEPORA MURRAYI. 211 



DESCRIPTION OF PLATES XIII & XIV. 



Illustrating Mr Sydney J. Hickson's paper " The Medusfe of 

 Millepora murrayi and the Gouophores of AUopora 

 and Distichopora." 



Gale. The calcareous skeleton or coenosteum. Gcen. The ccenosarcal 

 canals. In the superficial regions the canals are crowded with zooxan- 

 thellse. Ect. Ectoderm, coloured red. Eiid. Endoderm, coloured blue. 

 Gon. The ectodermal lining of the ampulla forming the wall of the 

 gonangium. Man. Manubrium of the medusa. Nemat. Large nema- 

 tocysts guarding the dactylopores. op. Operculum of modified ectoderm 

 cells covering the pore of the ampulla. Sperm. Spermarium. Sperm. S^ 

 Spermospheres or aggregations of spermospheres in the ectoderm of the 

 zooids. Sperm. S.,. Young spermospheres in the ectoderm of the canals. 

 Tent. Retracted tentacles. Umh. Umbrella of the medusa, consisting of a 

 solid endoderm covered on both sides by ectoderm. 



PLATE Xin. 



Millepora murrayi. 



Fig. 1. — Section through a retracted dactylozooid of Millepora mur- 

 rayi, showing a number of spermosiiheres {Sperm. S.^.) in the ectoderm of 

 the coenosarc, and in the ectoderm (Sperm. S-^.) at the base of the dactylo- 

 zooid. 



Fig. 2. — Section through a retracted dactylozooid, showing a single 

 small aggregation of spermospheres {Sperm. Sy) in the ectoderm at the 

 base of the dactylozooid. 



Fig. 3. — Section through a I'etracted gastrozooid, showing an aggrega- 

 tion of spermospheres in the ectoderm. The gastrozooids may be readily 

 distinguished from the dactylozooids by the presence of a mouth and by 

 the large endoderm cells, the perii^heral portions of which are filled with 

 mucus. Just below the gastrozooids may be seen a plate of vacuolated 

 ectoderm cells in section, which forms the last tabula of the gastropore. 



Fig. 4. — Section through a dactylozooid, showing a large aggregation of 

 spermospheres on its side in a condition very similar to that I have de- 

 .scribed in Millepora plicata (6). The spermospheres have caused a very 

 considerable depression in the dactylozooid, and are partially covered by 

 the surrounding parts. 



Fig. 5. — An aggregation of spermospheres at the peripheral extremity 

 of a dactylozooid. The tentacles {tent.) are visible. 



