12 



GUIDE TO THE CORAL GALI,ERY. 



Spongosplmra (Model 12) has three spheres, the outermost consisting 

 of a spongy reticulum ; the fine smooth spines in this model represent 

 pseudopods, but the pseudopod rays are beaded in the other models. 

 Spongosphcera streptamntlm, which is common on the surface of 

 warm-temperate and tropical seas all over the world, is about 

 ^Q of an inch in diameter. 



II. AcANTHARiA (Fig. i), and Model 13), with spherical porous 



Fig. 9.' 



Xipliacantha murrayana. Magnified 100 diameters. Skeleton only. 

 (After Wyville Thomson.) 



central capsule, with skeleton of "acauthin," constructed of 20 

 radiate spines proceeding from the centre, and always arranged in 

 fours according to a definite law known as " Miiller's Law." The 

 idea of a terrestrial globe with its parallels helps one to realize the 

 plan ; thus Haeckel calls the five fours equatorial, tropical and 



* From "The Voyage of the Challenger. — Atlantic." 



