221 



results ; and if the process continues for a short time, changes 

 familiar to those conversant with pathological alterations 

 occur upon a large scale. 



In discussing questions of this kind, involving such minute 

 details, we must, however, be most careful to avoid too hasty 

 generalization, and proceed by very slow steps ; and this is 

 more particularly necessary if it so happens that our inferences 

 in some measure accord with the views of speculative and 

 excited persons, who are always fancying that we are on the 

 eve of some grand discovery which is to revolutionise thought. 

 Many might perhaps infer from the arguments advanced, that 

 I incHne to the view that the lowest living forms are capable 

 of being produced by the retrograde development of higher 

 forms, and that bioj^lasm even very high in the scale of 

 organization, may produce forms of bioplasm approximating 

 more and more closely to the lowest constant forms of life 

 with which we are acquainted. A doctrine asserting that 

 by continual retrogression through ages the descendants of 

 the highest forms would gradually deteriorate until their 

 only remaining representatives were monads, Avould not be 

 very easily disproved, and might be supported by many 

 ingenious arguments. It is a view that doubtless would 

 recommend itself to some minds in the present day. 



On the other hand, it is quite conceivable that cells and 

 organisms may retrograde and produce various modified 

 forms, without giving rise to any of those particular forms 

 characteristic of the lower organisms with which we are ac- 

 quainted. Nay, cells of different organisms might give rise 

 to many different retrograde forms, and every one of these be 

 very different from one another. It is obviously possible 

 that there should be infinite advance and infinite retrogression 

 in multitudes of parallel lines, as it were, without the 

 resulting forms of any one line becoming identical with those 

 of another. Just as it is possible to conceive infinite advance 

 in the features of the dog, without any resemblance what- 

 ever to the human face resulting, and retrogression and dete- 

 rioration of the latter proceeding to any degree, and con- 

 tinuing for any length of time without the development of 

 the simian type of countenance. 



Sufficient allowance is not made by many thinkers for 

 the infinity of difference in structure and variety of change 

 possible in living forms, without the production of tAvo forms 

 exactly alike, or any indication of the merging of one set of 

 forms into another. It must not be forgotten for an instant that 

 from such a marvellous storehouse of facts as has been placed 

 at our disposal in nature, we may with very little ingenuity 



