THE MEDUSA OF MILLEPORA MURBAYI. 375 



The Medusae of Millepora murrayi and the 

 Gonophores of Allopora and Distichopora. 



By 



Sydney J. Hickson, 9I.A., D.Sc, &c.. 



Fellow of Downing College, Cambridge. 



With Plates XXIX and XXX. 



I. The Medusa of Millepora murrayi. 



In 1884, Quelch (11), while examining the structure of the 

 hard parts of a new species of Millepora (M. murrayi), dis- 

 covered a number of small cavities which he supposed to be 

 the receptacles of the ova or embryos like the ampullse of the 

 Stylasteridae. 



Professor Haddon has recently placed in my hands some 

 excellently preserved specimens of a species of Millepora 

 that he collected on the reefs of one of the islands in Torres 

 Straits. This species seems to be closely allied to Quelch's 

 Millepora murrayi, but the identification is a matter of 

 some difficulty, as the pieces at my disposal are small. 



On making a series of sections through a portion of a decal- 

 cified branch I discovered a number of medusiform structures, 

 each bearing a large saucer-shaped spermarium. They are 

 situated immediately beneath the surface, and covered by an 

 operculum of modified ectoderm cells. 



Sections made by von Koch's method of grinding hard and 

 soft parts together in solid Canada balsam show further that 

 these medusae exactly fit into the ampullar cavities of the 

 skeleton, and form the only explanation of their presence. 



VOL. XXXII, PART III. — NEW SEE. B B 



