366 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



for existence, any variation however slight, and from whatever cause 

 proceeding, if it be in any degree profitable to an individual of any 

 species in its infinitely complex relation to other beings, and to its 

 environment, will tend to protect that individual and will generally 

 be inherited by its offspring. Darwin calls the principle by which 

 each slight useful variation of an organism was preserved, the principle 

 of natural selection, in order to emphasize its relation to man's power 

 of selective breeding. For it is well known that by careful selection 

 of the stock, we can adapt organic beings to our own use through 

 the accumulation of slight but useful variations. Natural selection, 

 however, is a power constantly ready for action, and is as immeas- 

 urably superior to man's efforts as the work of nature is to that 

 of art. 1 



Darwin repeatedly insists on the fact that natural selection could 

 not have been effective, unless very long periods of time were allowed 

 for its complete action. It is evident that time must have been an 

 all-important factor if we are to suppose, that by the interaction of 

 the inherent properties possessed by the elements of living organic 

 matter, its structural arrangement became gradually modified in 

 such a way, that the existing classes of animals and plants have been 

 evolved out of it. For, as the late Prof. Huxley states, natural 

 selection implies not only the existence of organic matter, but also 

 its tendency to transmit its properties, and its tendency occasionally 

 to vary; and lastly, given the conditions of existence, that these 

 put together are the cause of the present and the past conditions of 

 organic nature. 



The only evidence we can bring to bear on the subject of the pro-! 

 gressive evolution of the animal kingdom is derived from a study of 

 their fossil remains, in the various geological strata of our own, and 

 other parts of the world. 2 The length of time these strata have 

 taken to form is an open question, but we may be sure that our 

 chalk rocks, for instance, consist of the shells of marine species of 

 animals, and that these remains of once living beings must have 

 taken long periods of time to have been deposited layer upon layer at 

 the bottom of the sea. Darwin states that the fineness of gradation in 

 the shells of successive substages of the chalk formations led him 

 to maintain the gradual as against the 'sudden evolution of species. 

 The fossil shells in these rocks have been thoroughly investigated by 

 Mr. A. W. Rowe, who states that "the white chalk of England offers 



1 On the Origin of Species by Means of Natural Selection, by Charles Darwin, M. A., 1859, p. 61. 



2 Many of the attacks made upon the hypothesis of natural selection have been founded on the imper- 

 fection of geological records to show the transitional links, which, according to this theory, must have 

 connected the closely allied species of animals. If, however, we take into account the perishable nature of 

 the bodies and limbs of these creatures, the probable changes that have occurred in the surface of the earth 

 since thay were deposited, and the imperfect state of our geological records, we can readily understand the 

 reason for there being missing links in the fossil remains of former geological periods. 



