ix CAUSES OF CHANGE OF OPINION 127 



direction of time. Powers of observation formerly limited to 

 the brief space of a few generations are now extended over 

 ages, which the concurrent testimony of various branches of 

 knowledge, of astronomy, cosmogony, and geology, show are 

 immeasurable compared with any periods of which we hitherto 

 had cognisance. We are enabled to trace, and every year, as 

 discovery succeeds discovery, with increasing distinctness, 

 numerous cases of sequences of modification running through 

 groups of animals in successive periods of time, such as the 

 gradual progress r.i the development and perfection of the 

 antlers of deer, from their entire absence in the earliest known 

 representatives of the type, through the simple conical or 

 bifurcated form, increasing in complexity as time advanced to 

 the magnificent many-branched appendages which adorn the 

 heads of some species of recent stags; such also as the 

 progressive modifications, so often described, beginning in the 

 short-necked, heavy-limbed, many-toed tapir-like animal of the 

 Eocene period, and ending in the graceful, long-necked, light- 

 limbed, single-toed horse of our own age, and numerous others 

 which time will not allow me even to mention. 



It would be impossible here to trace the history of the 

 effect of this enormous influx of knowledge upon the doctrine 

 of the separate origin and fixed characters of species ; to 

 narrate the scattered efforts of philosophical minds, dis- 

 contented with the former views, but not yet clearly seeing 

 the light ; to describe the slow and struggling growth of the 

 new views, amid difficulties arising from imperfections of know- 

 ledge and the opposition of prejudice, or to apportion to each 

 of those who by their labours have contributed to the final 

 result, his exact share in bringing it about. How much, for 

 instance, is due to the work and the writings of our illustrious 

 countryman, Darwin ? and how much to those who have 

 preceded or followed him ? All this forms an episode in the 

 history of the progress of human knowledge, which has been 

 abundantly chronicled elsewhere. 



The result may, however, be briefly stated to be, that the 

 opinion now almost, if not quite, universal among skilled and 

 thoughtful naturalists of all countries, and whatever their 

 beliefs upon other subjects, is that the various forms of life 



