208 STUDY OF NATURAL HISTORY. 



(143.) Of this law we have a familiar and a very- 

 beautiful illustration, in the annual revolution of the 

 seasons ; the months of which may be compared to a 

 series of beings following each other in close affinity. 

 If we begin with January, we trace the gradual deve- 

 lopement, first of spring, and then of summer ; from 

 thence we pass into autumn ; this season, again, melts 

 into the winter of December ; and we thus arrive 

 again at the point from which we first set out. So, 

 likewise, is a natural series of animals. If we begin 

 at any given species or group, and trace its connec- 

 tion to others, we find, that, after being conducted 

 through various modifications of the original type, 

 we are insensibly brought to that type again ; just 

 as if, by passing the point of a pin over the figure of 

 a circle, we should assuredly end where we began. 

 Now, as this hypothesis has been amply verified by 

 facts drawn from the animal and the vegetable 

 kingdoms, it has assumed the character and the 

 authority of a general law, and gives us no further 

 occasion to seek upon what principle the series of 

 nature is constructed. We shall have occasion, 

 hereafter, to dwell more particularlv on the com- 

 prehensiveness of this law, and the beauty of its 

 application throughout nature : at present, we merely 

 point it out to the student as that basis upon which 

 all his combinations must be built, and as a fixed 

 and determinate point from whence he may safely 

 begin his journey onward. 



(144.) The lowest combinations of objects, wherein 

 this law can be traced, are those groups of species 

 which were formerly denominated genera, but which 

 are called by the moderns sub-genera> — a term in- 



