MILLEPORINA 257 



It was found by Schaudinn ^ in the marine aquarium at Berlin in 

 water from Eovigno, on the Adriatic. It reproduces by gemma- 

 tion, but sexual oBgans have not been found. 



Another very remarkable genus usually associated with the 

 Eleutheroblastea is Polypodium. At one stage of its life-history 

 it has the form of a spiral ribbon or stolon which is parasitic on 

 the eggs of the sturgeon {Acipenser ruthenus) in the river Volga.^ 

 This stolon gives rise to a number of small Jlydra-like. zooids 

 with twenty tentacles, of which sixteen are filamentous and eight 

 club-shaped. These zooids multiply by longitudinal fission, and 

 feed independently on Infusoria, Eotifers, and other minute 

 organisms. The stages between these hydriform individuals and 

 the parasitic stolon have not been discovered. 



Order II. Milleporina. 



Millepora was formerly united with the Stylasterina to form 

 the order Hydrocorallina ; but the increase of our knowledge of 

 these Hydroid corals tends rather to emphasise than to minimise 

 the distinction of Millepora from the Stylasterina. 



Millepora resembles the Stylasterina in the production of a 

 massive calcareous skeleton and in the dimorphism of the zooids, 

 but in the characters of the sexual reproduction and in many 

 minor anatomical and histological peculiarities it is distinct. As 

 there is only one genus, Millepora, the account of its anatomy 

 will serve as a description of the order. 



The skeleton (Fig. 128) consists of large lobate, plicate, 

 ramified, or encrusting masses of calcium carbonate, reaching 

 a size of one or two or more feet in height and breadth. The 

 surface is perforated by numerous ppres of two distinct sizes ; the 

 larger — "gastropores" — are about 0*25 mm. in diameter, and the 

 smaller and more numerous " dactylopores " about 0'15 mm. in 

 diameter. In many specimens the pores are arranged in definite 

 cycles, each gastropore being surrounded by a circle of 5-7 

 dactylopores; but more generally the two kinds appear to be 

 irregularly scattered on the surface. 



When a branch or lobe of a Millepore is broken across and 

 examined in section, it is found that each pore is continued as a 



1 Sitzber. Ges. naturf. Freunde Berlin, ix. 1894, p. 226. 

 2 M. Ussov, Morph. Jahrl. xii. 1887, p. 137. 

 VOL. I S 



