CHAriEli YII. 



GENERAL CO^X'LU.SIONS. 



These have, perliaps, heeu sutKcieiitly indicated in an 

 incidental manner in tiie preceding pages; but it may be 

 well here to note some results of a less special chaiacter 

 and bearing on larger biological and cosmical question^.. 



With reference to the life of the Pleistocene period, one 

 can -jcarcely fail to observe that, whatever may have been 

 the lapse of geological time from the period of the oldest 

 boulder-clay to that in whicli we live, and great thougli 

 the climatal and geographical changes have been, we 

 cannot aHirm that any change, even of varietal value, has 

 taken place in any of tiie species of the above lists. 

 This appears to me a fact of extreme significance with 

 reference to theories of the modification of species in 

 geological time. Xo geologist doubts that tlie Pleistocene 

 was a period of considerable duration. The great eleva- 

 tions and depressions of the land, the extensive erosions, 

 the wide and thick beds of sediment, all testify to the 

 lapse of time. The changes which occurred were fruitful 

 in modifications of depth and temperature. Deep waters 

 were sliallowed, and the sea overflowed areas of laud. 

 The temperature of the waters changed greatly, so that 

 the geographical distribution of marine animals was 



