300 CONCLUSION 



such organisms are rather the best types of change and mutability. 

 That some Bacteria, Amoebas, Moulds, and other low organisms 

 should have lived in unbroken continuity through pre-Silurian 

 epochs, amidst all the changes of the Carboniferous, Triassic, 

 Oolitic, Cretaceous, and more recent geologic ages, with that 

 mutabihty as an essential characteristic which they are now seen to 

 display, and yet that they should have undergone little or no 

 alteration, seems too incredible to be seriously entertained. 



It is impossible to say that they have preserved their primitive 

 forms by reason of their existence in unchanging environments. 

 The very reverse of this must have been the fact ; and, even now, 

 such organisms are to be met with abundantly all over the face of 

 the earth, and in the most diverse situations. 



But, in accordance with the views advanced in this work, the 

 present-day existence of these organisms may be fully explained, 

 and is just what might be expected — if they are ever seething up 

 anew by Archebiosis and by Heterogenesis. These views, more- 

 over, leave us free to admit that their mutability is extreme, and 

 that their habitats are most diverse and world-wide — as all who are 

 well acquainted with such organisms should be free to acknowledge. 

 This very circumstance of the wide-spread distribution over the 

 earth of similar lowest types of life affords another test of the relative 

 validity of the two views. The facts brought forward in this work 

 seem to show that the intrinsic molecular composition and pro- 

 perties of the different varieties of living matter have much more 

 to do with the forms and structures of lowest organisms than mere 

 differences in their environment. Under the dominating influence 

 of ' organic polarity,' the several forms arising by Archebiosis and 

 Heterogenesis seem to unfold more or less immediately into such 

 and such simple organisms of common type. 



Then, again, the facts and arguments furnished by heterogenesis, 

 coupled with Herbert Spencer's views concerning ' physiological 

 units,' seem capable of affording a better explanation than has 

 hitherto been forthcoming of the sudden and abrupt variations in 

 higher plants and animals which are well known to occur — variations 

 that have been spoken of as ' discontinuous ' by Bateson, and as 

 ' mutations ' by De Vries, and which are often so marked as to 

 constitute sudden origins of actual new species of animals or plants. 

 These phenomena are, perhaps, the nearest approaches possible 

 among higher organisms to the still more marked transformations 

 described in this work as occurring among lower organisms. Yet 



