98 SEASON OP REST. 



difference, that they will hardly be suspected of being 

 relations ; yet the two forms may readily be traced 

 into each other, and this without going beyond the 

 evidence collected on our own shore. A change similar 

 to that caused by heat in the plant from the Canaries 

 is induced in this country by the very opposite con- 

 ditions of fresh water and muddy soil. The Fucus 

 balticus of northern writers, which is found in very 

 muddy enclosed arms of the sea, near high-water-mark, 

 and under the influence of fresh water, is a variety of 

 F. vesiculosw much resembling, especially when in 

 fruit, the starved variety found in the Canaries. This 

 affords us a striking instance of the opposite means 

 which Nature often employs to bring about the same 

 result, and may teach us that the adaptations which we 

 find in the various races of animals and plants have 

 some other controlling cause than the circumstances in 

 which the species find themselves. All we can determine 

 on this subject seems to be, that every species of animal 

 or plant has its natural condition, known only, in the 

 first instance, to the Author of Nature ; and that a de- 

 parture from that natural condition, in either direction, 

 will alter the character of the individual. But, until we 

 have tested the matter by direct experiment, we cannot 

 pronounce on the result. No one, by reasoning on the 

 subject, would be prepared for the fact that the heat of 

 the tropical sea would exercise the same transforming 

 power on a particular plant as the mud and fresh water 

 of a colder climate. A similar difference in the causes 

 which effect the same end, may be noticed in comparing 

 the means by which Nature provides a season of rest for 



