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II. Wissenschaftliche Mittheilungen. 



1 . On the Hydroid Stony Corals. 



By H. N. Moseley, F. R, S., Fellow of Exeter College Oxford, late Naturalist on 

 Board H. M. S. Challenger. 



In the Proc. R. Soc. No. 172. 1876, I published a preliminary 

 note on the structure of the Stylasteridae giving some of the results 

 obtained from an examination of the soft parts of six genera of the 

 family obtained by means of the trawl net in 600 fathoms off the 

 mouth of the Kio de la Plata. In the spring of this present year I pre- 

 sented to the Royal Society a detailed account of the structure of the 

 family Stylasteridae illustrated by eleven plates, w^hich will appear in 

 the second volume of the Transactions for 1878. The results attained 

 are summed up shortly as follows. 



The Milleporidae and Stylasteridae are both essentially Hydrozoan 

 in nature and not Anthozoan and the two families agree in many 

 details of structure. They may, for the present at least, be placed to- 

 gether in a suborder Hydrocorallinae. The generative organs of the 

 Milleporidae are at present unknown ; their discovery may perhaps 

 necessitate a separation of the two families. 



The following are the characters of the suborder Hydrocorallinae 

 H. N. M. (Phil. Trans. R. Soc. Vol. 167. 1877. p. 132). 



Compound Hydroid stocks, growing by gemmation. liydrophyton 

 consisting of a meshwork of ramified coenosarcal canals, composed of 

 an ectoderm and pigmented endoderm, lodged within channels per- 

 meating a hard calcareous support, »corallum«, which is deposited by 

 the ectodermal investment of the canals, and forms masses of very 

 various shape. Surface of the Hydrophyton covered with a continuous 

 layer of ectoderm. Zooids of two forms, the one provided with a mouth 

 and gastric cavity, »gastrozooid«, the other mouthless and simply ten- 

 tacular in function, »dactylozooid«. Tentacles, when present, mostly 

 with knobbed extremities. A well-defined muscular layer present in 

 the zooids. Zooids lodged within chambers excavated in the substance 

 of the Hydrophyton, »gastropores«, and »dactylopores«, lined by reflec- 

 tions of the surface layer of the ectoderm, forming the »sacs« of the 

 zooids. Zooids of the two forms either scattered irregularly over the 

 surface of the stock; or gathered into groups more or less regular, in 

 each of which a centrally-placed gastrozooid is surrounded by a ring of 

 dactylozooids. Cavities of zooids communicating with coenosarcal 

 meshwork by large canal offsets. 



The Family Milleporidae may be thus distinguished. 



