HYDROZOA. 



49 



termed gastropores, and the dactylozooids in smaller pits termed dacty- Cases 2, 4. 

 lopores, the pores being usually arranged in systems (Figs. 15 and 18.) 



MiLLEPORiD^. MiUepora forms massive laminate or branched Case 4. 

 growths, and presents a great variety of forms ; but, according to Prof. 

 Hickson, there are no definite specific characters separating one form 

 from another, and consequently we must regard the forty or more 

 so-called species as mere variations of only one species, viz., MUlepora 



Fig. 10. 



Monocaulus imperaior, upper third. (Much reduced.) 



alcicornis, or the Stag's Horn Millepora. He would call, for instance, 

 M. verrucosa (Case 4, upright portion) M. alcicornis, facies verrucosa. 

 It seems that an embryo settling down on a broad surface with 

 room to spread forms a laminate growth, such as the typical M. 

 alcicornis or M. complanata (Case 4) ; but if it settles on a small 

 object it tends to form a branching growth. MiJlepora often encrusts 

 old bottles, &c. ; in Case 3a a delicate network of Fan Coral is exhibited 

 coated with a thin crust of MiUepora alcicornis. Systems consisting 

 of small gastropores, surrounded by irregular circles of about six still 



