Lecture XXX. 277 



selves more readily for preservation, trace the animal kingdom 

 from its simple beginnings to its present marvellous complexity. 

 Thus in this great book we find written in bold outline the history 

 of organic evolution. While in most instances the record is only 

 in outline some details of fascinating interest have been preserved. 

 Thus botanists have been able to trace the origin of seed plants 

 from fern-like ancestors, and their investigations have made us ac- 

 quainted with the form and the minute structure of many seed- 

 bearing ferns, which are genetic links between the present seed 

 plants and primitive ferns. Very recently fossils have been found 

 probably illustrating similar connecting-links between the mosses 

 and ferns. Similar discoveries of much more complete connecting 

 series in the animal kingdom were made in the last century, so that 

 to-day the geological record stands as one of the most convincing 

 proofs of the theory of evolution. 



While naturalists are pretty well agreed that the vast numbers 

 of species, as we see them on the earth at the present day, have 

 arisen by descent from pre-existing less numerous and more simple 

 forms, there is no such general agreement as to the manner in 

 which this evolution and these transformations of species have come 

 about. 



Darwin's great contribution towards the solution of this problem 

 was the theory of natural selection. And it is to this theory that 

 the name of Darwinism is properly applied. 



Starting from the observations that the individuals of the pro- 

 geny of any two parents, or of any single bisexual individual, differ, 

 or vary, among themselves, and that, as many variations are heri- 

 table, human selection can produce special races from a common 

 stock, Darwin conceived that if some natural cause acting in a 

 similar manner to human selection could be shown, then an ex- 

 planation would be given as to how a certain line of descendants of 

 a species is caused to diverge more and more from its average 

 character until a new species is formed. Reflecting that many 

 more individuals are born in 'each species than can come to maturity, 

 and that in the struggle for existence many perish, while only the 

 fittest or those endowed with variations which enable them to com- 

 bat better external and internal conditions survive, Darwin recog- 

 nised in this weeding-out process a natural factor comparable to 

 human selection in the artificial production of various breeds and 

 races. This factor he called Natural Selection. 



None can deny that natural selection operates to eliminate the 

 unfit, but biologists are not agreed as to how far the observed 



