THE MEDUSiE OP MILLEPOEA MURRAYI. 405 



DESCRIPTION OF PLATES XXIX & XXX, 



Illustrating Mr. Sydney J. Hickson's paper " The Medusae 

 of Millepora murrayi and the Gonophores of AUo- 

 pora and Distichopora/^ 



Culc. The calcareous skeleton or ccenosteum. Coen. The ccenosarcal canals. 

 In the superficial regions the canals are crowded with zooxanthellse. Ed. Ecto- 

 derm, coloured red. End. Endoderm, coloured blue. Gon. The ectodermal 

 lining of the ampulla forming the wall of the gonangium. Mati. Manubrium 

 of the medusa. Nemat. Large nematocysts guarding the dactylopores. 

 op. Operculum of modified ectoderm cells covering the pore of the ampulla. 

 Sperm. Spermarium. Sperm. S^. Spermospheres or aggregations of spermo- 

 spheres in the ectoderm of the zooids. Sperm. S... Young spermospheres in 

 the ectoderm of the canals. Tent. Retracted tentacles. Umb. Umbrella of 

 the medusa, consisting of a solid endoderm covered on both sides by ectoderm. 



PLATE XXIX. 

 Millepora murrayi. 



Fig. 1. — Section through a retracted dactylozooid of Millepora murrayi, 

 showing a number of spermospheres {Sperm. S^-) in the ectoderm of the cceno- 

 sarc, and in the ectoderm {Sperm. Sy) at the base of the dactylozooid. 



EiG. 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 retracted gastrozooid, showing an aggregation 

 of spermospheres in the ectoderm. The gastrozooids may be readily dis- 

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

 large endoderm cells, the peripheral 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 described 

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

 siderable 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 {teuL) are visible. 



Fig. 6. — An aggregation of spermospheres {Sperm. S^) at the peripheral 



