150 



MEDITERRANEAN PROVINCE. 



Mediterranean, and as far south as the Canaries, 

 but which has not yet been recognised as a British 

 species. 



When the animals of different sea-zones are 

 brought together and compared, it is constantly 

 found that variation in size is a marked character 

 with reference to species which are strictly identi- 

 cal ; the British naturalist finds constant occasions 

 for noting facts of this kind, when pursuing his re- 

 searches away from his own immediate seas. With 

 respect to Echinoderms, Ophiura texturata and Echi- 

 nus lividus, from the south coasts of France, Spain, 

 and the Mediterranean, exceed ours in size, and we 

 have a still more remarkable instance if, as is sup- 

 posed, the great Echinus melo be the same with our 

 E. sphcera. On the other hand, Spatangus purpu- 

 reus attains a much greater size on the coast of 

 Norway than it does in the Mediterranean. Size 

 and numerical abundance of any given form may 

 be taken as the surest indication that it is at home 

 there, or in its proper zone ; true northern forms 

 degenerate and become scarce as they range south, 

 just as southern ones do as they occur north. The 

 directions in which such changes as these take place 

 should be carefully noted, for these forms are not 

 depauperized stragglers from their natural settle- 

 ments, but rather the remnants, and indications of 

 changed conditions, and are of the same value to 

 the naturalist that the lingering communities of 

 isolated races of man are to the ethnologist. 



