CHAPTER IV 



free and fixed animals 

 (eleutherozoa and statozoa) 



We may now consider briefly another couple 

 of essential properties of plants and animals, and 

 note once more how the contrasted qualities are 

 paralleled within the limits of the animal kingdom 

 alone. The power of automatic locomotion, of 

 executing free movements of translation from 

 place to place, is one of the distinctive privileges 

 of animals. The property of becoming rooted 

 to the soil, and of undergoing perennial growth 

 and regeneration, is the no less picturesque 

 attribute of plants. 



So inseparable from animal life did mobility 

 appear, that the sponges, hydroids, corals, and 

 bryozoa were formerly classed together as 

 zoophytes, and were either believed to be plants 

 of a peculiar kind or, as the name implies, to 

 partake of the nature of both plants and animals. 

 The purely animal nature of the coral polyps 

 was established in the middle of the eighteenth 

 century, that of sponges towards the middle of 



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