SIX-RAYED POLYPS 



348i 



Although the mushroom corals are considered to be individuals, reproducing them- 

 selves by means of eggs, both budding and division into halves occur exceptionally; 

 in the former case the 

 buds sooner or later be- 

 coming detached. In 

 some there is an alter- 

 nation of generations, 

 leading to the forma- 



A BRANCHING CORAI,, Dendrophyllia. 



A. Terminal branch of a stock (natural size); B. Longitudinal section of a single polyp (magnified). 



tion of compound stocks. In the illustrated form true mushroom corals are pro- 

 duced at the ends of the branches; at a one has 

 become detached, and the others are in different 

 stages, the youngest being nearly cylindrical, like 

 a typical polyp whereas the older ones spread 

 out like a typical Fungia. When a bud has fallen 

 off, the stem seems capable of developing another. 

 This is the asexual generation, reproduction by 

 eggs being the sexual generation. Lastly, certain 

 solitary corals have recently been discovered in the 

 deep sea, where, on acount of the presence of carbonic 

 acid in sufficient quantities to make itself felt, there 



is little lime. On 

 this account the 

 calcareous skele- 

 ton is generally 

 distinguished b y 

 great delicacy. A 

 deep-sea coral with 

 such a delicate 

 skeleton ( Lepto- 

 penus) , found off 

 the east coast of 

 South America 

 A MADREPORE CORAI, (Madreporo, verrucosa). a * a depth of over 



In the section B the canals which connect the polyps through the stony skeleton are seen. & mile, IS SI1OW11 



