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CHAPTER XXII. 

 GENERAL CHARACTERS OF RADIATA. 



1080. THE Radiated subdivision of the Animal Kingdom 

 includes all those animals, in which there is a regular disposition 

 of similar parts around a common centre, as in the Star-fish 

 (Fig. 708), or Sea- Anemone (Fig. 719). In the most character- 

 istic forms of this group, these parts are but repetitions of each 

 other; and one or more of them may be removed without injury 

 to the functions of the rest. It is by no means uncommon to 

 meet with Star-fish, which, by some accident, have been de- 

 prived of a ray, and yet appear to have suffered but little incon- 

 venience from the loss. In most of the Radiata, the parts so 

 lost are replaced by a new growth; and not unfrequently it 

 would appear that these parts may themselves reproduce the 

 whole structure. Here, then, is an important character, which 

 evidently displays an affinity with the Vegetable Kingdom. In 

 Plants we observe that the whole structure is made up of an 

 assemblage of similar parts the leaf-buds which may almost 

 be regarded as distinct individuals ; for though, whilst associated, 

 they contribute to form a structure which is common to all, and 

 share alike in performing the functions of that structure, yet 

 they may be separated from it and from each other without the 

 loss of their vitality, if placed in circumstances favourable to 

 their growth under this new condition. We shall presently ob- 

 serve that, in the POLTPIPERA, compound structures are pro- 

 duced by the association of individuals, which have very nearly 

 the same relation to each other, and to the whole mass, as exists 

 amongst the buds of a tree, and between these and the woody 

 trunk and branches. 



1081. But it is not only in this repetition of similar parts, 

 that we may trace an affinity between the RADIATA and Plants. 



