IWEKTEBRATE ANIMALS. 



the latter organs, but are destitute of a mouth. The body-cavities 

 of all the zooids are placed in communicatiou by means of canals 

 which ramify in the sjaongy skeleton. 



Fig. 46. — Enlarged view of a portion of the surface of a living colony of MiUepora 

 nodosa, showing the expanded zooids of a single system, a, Central " gastrozodid " ; 

 5, One of the niouthless "dactylozodids." (After Moseley.) 



Other living Hydrocorallines are the coral-like Stylaster, Allopora, 

 &c. Closely allied to the recent types above mentioned is a great 

 series of fossil and wholly extinct organisms, of which Stromatopora 

 may be regarded as the central form. 



