HYDROZOA. 



47 



stems giving oflF whorls of slender branchlets bearing the minute cups Case 3b. 

 and still more minute funnel-shaped nematophores. 



A. ramosa (Case 3b) has branched stems. 



In Aglaophenia pluma, the "Podded Coralline," the reproductive 

 capsules are protected by a pod-shaped receptacle formed by modified 

 branchlets which curve round and meet. 



Aglaophenia urens* from Java, is named on account of its severe 

 stinging properties. Some species of this genus living in the tropics 

 attain a height of several feet, and it is dangerous to come in contact 

 with them. 



Fig. S. 



Hydractinia echinata on a shell of a whelk inhabited by a Hermit Crab. 

 (Natural size.) 



II. HYDROCORALLINiE OR CORAL-LIKE HYDROZOA. 



The Hydrozoa of this group resemble the Reef Corals in forming Cases 2, 4. 

 a calcareous skeleton ; indeed, the Hydrocorallinte were supposed 

 to belong to the same class (Anthozoa) as the Corals, till Agassiz 

 showed that Millepora was a true Hydrozoon. Later, Moseley, in his 

 classical work on the Challenger Hydrocorallin*. confirmed Agassiz' 

 results, and proved that the Stglastoridm were also Hydrozoa. In 

 all the Hydrocorallines two forms of polpys (Fig. 16) occur, viz., 

 gastrozooids, with mouth and stomach, and tentacle-like dactylo- 

 zooids without a mouth ; the gastrozooids are contained in pits 



