56 PICTURESQUE SKETCHES 



being ultimately succeeded by a group (the gastero- 

 pods) of much lower organization, although admirably 

 fitted for the work they had to perform. We shall 

 see hereafter that the course of development of the 

 fishes and reptiles was very similar to this ; so that 

 there is no evidence of these animals having gradually 

 passed into one another, or of any such order of suc- 

 cession having been a part of the plan adopted by the 

 great Director of the universe.* 



Since it is the fact, that, according to some general 

 law, species of animals are introduced, last only for 

 a limited period, and are then succeeded by others 

 performing the same office, it will readily be seen that 

 in any group of strata the absence of a certain number 



* I have dwelt the more earnestly on this subject, because there ap- 

 pears to be a strong tendency in the minds of many persons to conclude, 

 that since the Invertebrata appear to have been first introduced, and to 

 have been in course of time succeeded by the vertebrated animals in 

 something of the order of their organization, there was a succession and 

 a gradual development of higher types of existence in a certain order of 

 creation. So far as Geology in its present state affords evidence on this 

 subject, the" facts seem decidedly opposed to any such view ; and I make 

 this statement the more unhesitatingly, because I find that it perfectly 

 accords with the conclusions arrived at by one of the most philosophical of 

 living naturalists, who brings to a close his investigation concerning the 

 extinct Reptiles in the following manner : 



" Thus, though a general progress may be discerned, the interruptions 

 and faults, to use a geological phrase, negative the notion that the pro- 

 gression has been the result of self-developing energies adequate to a 

 transmutation of specific characters ; but, on the contrary, support the 

 conclusion, that the modifications of osteological structure which charac- 

 terise the extinct reptiles, were originally impressed upon them at their 

 creation, and have been neither derived from improvement of a lower, nor 

 lost by progressive development into a higher type." Professor Owen's 

 Report on British Fossil Reptiles ; Report of Eleventh Meeting of the British 

 Association at Plymouth, 1842, p. 202. 



