PROGRESS OF ANIMAL LIFE, 95 



beings are held together in a series of near and gradual con- 

 nexions. 



This discovery, amid the relics of past creations, of links 

 that seemed wanting in the present system of organic na- 

 ture, affords to natural Theology an important argument, 

 in proving the unity and universal agency of a common 

 great first cause ; since every individual in such a uniform 

 and closely connected series, is thus show^n to be an integral 

 part of one grand original design. 



The non-discovery of such links indeed, would form but 

 a negative and feeble argument against the common origin 

 of organic beings, widely separated from one another; be- 

 cause, for aught we know, the existence of intervals may 

 have formed part of the original design of a common crea- 

 tor ; and because such apparent voids may perhaps exist 

 only in our own imperfect knowledge ; but the presence of 

 such links throughout all past and present modifications of 

 being, shows a unity of design which proves the unity of 

 the intelligence in which it originated. 



It is indeed true tiiat animals and vegetables of the 

 lower classes prevailed chiefly at the commencement of 

 organic life, but they did not prevail exclusively ; we find in 

 rocks of the transition formation, not only remains of 

 radiated and articulated animals and mollusks, such as 

 Corals, Trilobites, and Nautili ; but we see the vertebrata 

 also represented by the Class of Fishes. Reptiles have 

 been found in some of the earliest strata of the secondary 

 formations.* In the footsteps on the New Red sandstone, 

 we have probably the first traces of Birds and Marsupialia. 

 (See PI. 26a. and 26'.) The bones of Birds occur in the 

 Wealden formation of Tilgate forest, and those of Marsu- 

 pialia in the Oolite at Stonesfield. (See PI. 2. Figs. A. B.) 



* E. g. In the Magnesian Conglomerate of Durdham Down near 

 Bristol, and in the bituminous marl slate, (Kupferschiefer) of Mansfield in 

 the Hartz. 



