1334 THE STORY OF THE UNIVERSE 



tentacles, but to a simple pith with many threads 

 or stinging cells in it. It is more or less like a long 

 tongue, and is placed among the cups with polypes, 

 and it is evidently an instrument for capturing 

 minute creatures. The Sickle-beard is one of them. 



But one of the most singular of these delicate 

 creatures lives in very numerous colonies, on such an 

 unexpected place as the outside of the shell tenanted 

 within by a wandering hermit-crab. It is called 

 Hydractinia. The Hydractinia has a kind of crust 

 for its formation, with tubes in it, and out from them 

 comes a white film, which, under a magnifying- 

 glass, presents a number of stems and polypes. Each 

 one has at its free part a club-shaped end, which has 

 several rows of tentacles around it. These, often 

 twenty-five in number, are, like the stem, very irri- 

 table, flexible, and are covered with a sticky matter. 

 The club is hollow within, for the stomach, and food 

 gets in by the top, where the horny skin appears to 

 be absent. 



The tentacles are rather sharp, and when they are 

 half-contracted they often appear to have a knob at 

 the end, otherwise they are stuck out and are like so 

 many thick threads. The stalk which supports the 

 conical-shaped head has a thin and wrinkled skin 

 with sharp, dot-like points on it, and probably they 

 secrete a sticky substance. The polypes thus formed 

 cluster together like so much moss on the shell, and it 

 would appear, if not in the English species, certainly 

 in one which frequents the American coasts, that 

 some groups are male and others female. But there is 

 no doubt, from the researches of Mr.Moseley, F.R.S., 



