Histology of the Soft Parts of Astraeid Corals. 



By 

 0. 3Iatthai, 3I.A., 



Mackinnon Student of the Royal Society during the years 1914-17. 



With Plates 7 and 8. 



The following account of the histology of the soft parts of 

 the Astraeidae is supplementary to the description given 

 in the Introduction to my paper on 'A Revision of the Eecent 

 Colonial Astraeidae possessing Distinct Corallites ' (25, pp. 1-32). 

 It is based on the study of a large number of polyps belonging 

 to various Astraeid species of the Indo-Paciiic and Atlantic 

 regions, particularly of Fa via favus (Forsk.), Fa via 

 hululensis (Gard.), Coeloria daedalea (Ell. and Sol.), 

 Leptoria gracilis (Diina), Eusmilia aspera (Dana). 

 During a short stay at the Carnegie Marine Biological Station 

 at Tortugas (July 16-August 2, 1915), living colonies of all 

 coral species of that locality were kept under observation, 

 but at that time larvae were extruded only from colonies of 

 F a V i a f r a g u m (Esp.). These were fixed at different intervals 

 during the free-swimming stage — from eight hours to about 

 ten days — in Flemming's fluid, corrosive acetic solution, and 

 Bouin's fluid, and were subsequently sectioned serially to 

 thicknesses of 4 M, 6 M, 8 M, and 10 fx in order to compare their 

 histology with that of adult colonies. No larvae of any species 

 were obtained during a subsequent visit to the Bermudas 

 (Aug. 20 - Sept. 14). Solid embryos lying in the coelen- 

 teric cavities of polyps from a colony of Favia fragum, 

 which Dr. Vaughan forwarded to Professor Gardiner from 

 South Bight, Btihamas, and which have been sectioned, were 

 also studied. 



The colonies from the Indo-Pacilic region were fixed in 

 saturated solution of corrosive subhmate and in formic aldehyde 

 poured into sea- water ; those from the Atlantic region were 



