78 GENERAL EVOLUTION. 



Vertebrata and other branches, as we already can in part prove. 

 And I have no doubt that the synthetic types, which represent 

 modern orders, have existed in a generic relationship subordinate 

 to the plan of the synthetic class, and that the latter have existed 

 as genera only, of the type of the great branch. This is not ideal. 

 We only have to look to our extinct ganoids, Archegosaurs, Laby- 

 rinthodonts, Compsognathus, Archseopteryx, Ornithorhynchus, 

 etc., to realize these facts. 



The first genera then formed a scale of which the members 

 were identical with the undeveloped stages of the highest, and 

 each to each according to their position. 



Such a series of antitypic groups having been thus established, 

 our present knowledge will only j)ermit us to suppose that the 

 resulting and now existing kingdoms and classes of animals and 

 plants were conceived by the Creator according to a plan of his own, 

 according to his pleasure. That directions or lines of development 

 toward these ends were ordained, and certain laws applied for their 

 realization. That these laws are the before-mentioned law of ke- 



TARDATIO]Sr AND ACCELERATION ; and laW of NATURAL SELECTION. 



The first consists in a continual crowding backward of the 

 successive steps of individual development, so that the period of 

 reproduction, while occurring periodically with the change of the 

 year, falls later and later in the life history of the species, confer- 

 ring upon its offspring features in advance of those possessed by 

 its predecessors, in the line already laid down partly by a prior 

 suppression on a higher platform, and partly, as above supposed, 

 by the special creative plan. This progressive crowding back of 

 stages is not, however, supposed to have progressed regularly. On 

 the contrary, in the development of all animals there are well- 

 known periods when the most important transitions are accom- 

 plished in an incredibly short space of time (as the passage of 

 man through the stages of the aorta-bows, and the production of 

 limbs in Batrachia anura) ; while other transitions occupy long 

 periods, and apparently little progress is made. 



The rapid change is called metamorphosis ; the intervening 

 stages may be called larval or pupal. The most familiar examples 

 are those which come latest in life, and hence are most easily ob- 

 served, as in the insects and frogs. When, during the substationary 

 period, the species reproduces, a constancy of type is the result ; 

 when the metamorphosis only appears at the period of reproduc- 

 tion, a protean type is the result ; when the metamorphosis is crowd- 



