THE VEGETABLE AND ANIMAL KINGDOMS. 155 



experience were extended, especially since the world presents 

 us with results, which can only be naturally accounted for in 

 this manner. It is here a fact to be specially remarked, that 

 the greatest variability, the most striking instances of transi- 

 tion or intercommunion of forms, are offered in the lower 

 grades of Being. In these departments of nature, generation is 

 rapid and abundant, in comparison with the reproduction of the 

 higher forms. What requires perhaps a century in the one case 

 (say a series of three generations) will be accomplished in a day 

 in the other. Nothing, therefore, seems more natural than that 

 phenomena connected with the reproduction of the higher 

 animals should require a much longer time to be evolved than 

 those connected with the lower. The time may be, in the one 

 case, such as to fall within our range of observation (and this 

 range, as far as scientific accuracy is concerned, is but a day), 

 while in the other case it may be, and indeed, on a just com- 

 parison, we should expect it to be, beyond even the whole 

 space of what is called the historical era. Such is precisely 

 the point to which the present theory would lead us. We see 

 that permanency of specific distinctions in the higher organisms 

 might sink, as it has done in so many of the lower, ifive had 

 as long a time to observe their reproductive history, as would, in 

 embryology, be equivalent to the space of time during which we 

 have observed the humbler creatures. We see this persistency, 

 and think it fixed, exactly as men have hitherto seen the solar 

 position in the universe. We advance among the stars at the 

 rate of two millions of millions of miles a year ; but astro- 

 nomers tell us that it would take ninety millions of years to 

 enable us to pass through the whole, even at this rapid rate. 

 Well, therefore, might the unassisted eye and unexamining 

 intellect presume the place of the solar system to be fixed, for 

 it is evident that no human tradition could record changes 

 indicating the translation. Yet we do pass on to Hercules, 

 although forty centuries failed to remark the circumstance. 

 So may specific distinctions in the higher animals have been 

 changed in the course of the vast periods which geology shows 

 to have elapsed since the commencement of organization upon 

 earth, although, during that inappreciable segment of the great 

 cycle which has passed since man woke to the mysteries of 

 nature, no single transition of the kind might have been 

 observed. The whole case reminds us greatly of the objection 

 which stood against the earth's motion from the days of 

 Aristarchus downwards, that there ought in that case to be 



