FORAMINIFERAN AND OTHER CORALS 191 



cells which appear to be of the general nature of amoebo- 

 cytes take upon themselves the function of secreting calcium 

 carbonate (calcocytes), and it is with these remarkable cells 

 that the crypts are filled. 



AsTROSCLERA. — Another very remarkable calcareous 

 structure which seems to be undoubtedly the production 

 of a sponge is Asirosclera willeyana} 



The type specimen from Lifu is a little hard calcareous 

 knob about 8 mm. in height by 5 mm. in diameter. The 

 stem is cylindrical and smooth with a spreading base attached 

 to a dead coral ; the upper end is convex and scored by an 

 irregular labyrinth of pits and grooves. j\ J\ a A 

 A specimen from Funafuti is shaped "'™«^^''~^ ■' - 

 like a short-stalked fungus with a disc 

 20 mm. in diameter. Other specimens 

 are more irregular in shape, but they 

 all show grooves and pits on the upper 

 free surface. 



In a vertical section the interior of 

 the coral is seen to be penetrated by a 

 system of anastomosing channels, many 

 of which have a longitudinal direction 

 and eventually open to the exterior in 

 the pits of the upper surface. In fresh 

 specimens the soft tissues of the sponge 

 cover the distal surface and, extending 

 beyond it some little distance down the stem, penetrate into 

 the anastomosing channels in the corallum. 



Astrosclera has hitherto been found in 35 fathoms of 

 water off Lifu in the Loyalty Islands, and in 100 fathoms 

 off Funafuti in the Ellice group. 



Petrostroma schulzei. — Another sponge which forms 

 a hard calcareous structure is Petrostroma schulzei, found at 

 depths of 100-200 fathoms of water off the coast of Japan. 

 According to Doderlein "^ it represents a distinct family of 

 calcareous sponges which he calls the I.ithonina. 



I'"iG. 98. — Diagram to 

 illustrate the strueture of 

 Merlia. X4odiams. 



1 J. J, Lister in Willcy's Zool. Results, Part IV 

 Natural History, vol. i. p. 194. 



- Doderlein, Zool. Jahrb., Syst. X., 1898. 



1900 ; and Cambridge 



