CHAP, in.] PROTECTIVE ARRANGEMENTS. 97 



are to a great extent due to the various successful and 

 unsuccessful modifications of the crude ideas of nutrition 

 and reproduction that were contemporaneous with the 

 appearance of the simplest members of the Vegetable 

 Kingdom. 



The most complete and highly differentiated protec- 

 tive arrangements are met with in Phanerogams, and 

 even here the aquatic forms show least specialization in 

 this respect. Amongst terrestrial species the modes of 

 protection even against the same enemy are very varied 

 in the different species. Leaving for the present the con- 

 trivances for protection in connection with the repro- 

 ductive portion (that will be described later on) , we find 

 the various arrangements for protecting the individual to 

 fall under two headings protection against climate, and 

 protection against living enemies. As would be expected, 

 the two divisions meet and overlap at many points, for it 

 may be stated as a general rule that every case of spe- 

 cialization originates for the performance of a certain 

 specific function, and if the experiment proves a success, 

 and consequently becomes a permanent feature, further 

 modifications are superadded which may serve purposes 

 widely different from the original, and thus by various 

 modifications and amendments, such structures, that 

 originated in a simple form and for a specific purpose, 

 become extremely complicated, not only by the addition 

 or modification of parts that still perform functions of 

 service to the plant, but also by the remains in various 

 stages, of structures that at one time performed work of 

 real service to the individual, but which for some reason 

 or other have been superseded; but such structures, 

 when once fully evolved, cannot be at once arrested by 



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