888 Agassiz—Paleontological and Embryological Development. 
growth or of historic development, repeating in a different di- 
rection the same phases. Does it then pass the limits of analogy 
wide of the facts as far as ‘they are known, and seem so readily 
to ignore them. e moment we leave out of sight the actual 
succession of the fossils and the ascertainable facts of postem- 
bryonic development, to reconstruct our genealo 
boasts for its very creed a belief in nothing which is not war- 
ranted by common sense should descend to such trifling. 
The time for genealogical trees is passed; its futility can, 
perhaps, best be shown by a simple calculation, which wil 
point out at a glance what these scientific arboriculturists are 
attempting. Let us take, for instance, the ten most character- 
istic features of Kchini. The number of possible combinations 
which can be produced from them is so great that it would 
take no less than twenty years, at the rate of one new combi- 
nation a minute for ten hours a day, to. pass them in review. 
Remembering now that each one of these points of structure is 
itself undergoing constant modifications, we may get some idea 
of the nature of the problem we are attempting to solve, when 
seeking to trace the.genealogy as understood by the makers of 
