CHAPTER IV. 



SEA-ANEMONES AND THEIR ALLIES. 



Differences between sea-anemones and zoophytes Four common sea- 

 anemones, their habits and characters Variation in sea-anemones 

 "Dead men's fingers" in life and after death The sea-pen 

 The Jelly-fishes Life-history of Aurelia Relation to Lucenaria 

 The Ctenophora, or "iridescent fire-globes." 



SO far we have been concerned with the simplest of the 

 Coelentera, where any complexity which may occur is 

 the result of the combination of individuals, and not of the 

 characters of the individuals themselves. Furthermore, as 

 we have repeatedly emphasised, the individuals are always 

 small, often very small, and alternation of generations is 

 always clearly indicated, though there is a tendency for it 

 to become suppressed. In all the cases we discussed where 

 the alternation disappears, it is the active medusoid stage 

 which is lost. The second class of Coalentera, which we 

 are to consider in this chapter, is in many respects very 

 sharply contrasted with the Hydrozoa. The individuals are 

 often large ; colonies, in our seas at least, are relatively less 

 frequent; the structure of the individual is more complex 

 than in the Hydrozoa; there is either no trace of alternation 

 of generations, or, where it occurs, the active jelly-fish stage 

 tends to be accentuated at the expense of the stationary 

 stage. This class is often called the Scyphozoa, and is held 

 to include the sea-anemones and their allies (Anthozoa), and 

 the big jelly-fish. By some authorities, however, the jelly- 

 fish are placed in a separate class. As we shall be very 

 little concerned with the jelly-fish we need not discuss the 

 question of their position, but may merely emphasise their 

 distinctness from the swimming-bells of the Hydrozoa, 

 which are much smaller and less complex. 



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