PROOFS, ILLUSTRATIONS, AUTHORITIES, ETC. xxvii 



So much the worse for Mr. Miller's opposition to the development 

 hypothesis, if Professor Agassiz (perhaps the most philosophical of 

 living zoologists) is to be trusted. The development hypothesis 

 would, according to that philosopher, demand bulk in the initial 

 animals of eachline, and it is much beholden to Mr. Miller for the 

 help he has thus given it, while doing his best, certainly under great 

 difficulties, to show its baselessness. 



11. VARIABILITY OF SPECIES. 



The following remarks occur in a series of papers in the Phyto- 

 logist, being from the pen of a distinguished botanist, Mr. H. C. 

 Watson : 



" We seem to be justified in asserting that our knowledge of the 

 present events in nature, taken by itself, should incline us to a con- 

 clusion which is directly adverse to the theory of 'progressive 

 development,' or ' transition of species,' yet, without affording us 

 any actual disproof of that theory. It is otherwise when our range 

 of thought embraces the vastly wider space of time, the events of 

 which are investigated by geologists. There we find ample evidence 

 to justify the conclusion that different species succeeded each other. 

 And no better mode of accounting for this succession has been sug- 

 gested, than the hypothesis that one species passed into another, under 

 changing external conditions. Supposing this transition of species 

 to have taken place very gradually, and through a long series of 

 descents, it would not require more rapid change (from central types 

 into varieties, and from a less variety into a greater), than we see 

 actually occurring in the production of varieties at the present period 

 of the earth's history. Could we ascertain that some varieties will 

 continue to vary from their central type through many successive 

 descents, and that, as they become less similar to their original 

 central type, the tendency of ' like to produce like' will overpower 

 and supersede the tendency to revert to the original central type ; 

 in this case, we might hold the ' transition of species' to be a theory 

 founded on facts." 



An eminent naturalist of the United States makes some observa- 

 tions tending to the same point : " Although we may not," he says, 

 " be able artificially to produce a change beyond a definite point, it 

 would be a hasty inference to suppose that a physical agent, acting 

 gradually for ages, could not carry the variation a step or two farther; 

 so that, instead of the original (we will say) four varieties, they 

 might amount to six, the sixth being sufficiently unlike the earlier 

 ones to induce a naturalist to consider it distinct. It will now have 

 reached the limit of its ability to exist as the former species, and 

 must be ready either to develop a new dormant organic element, or 

 die ; if the former is effected, the osculating point is passed, and the 

 species established upon the few individuals that were able to survive 



