324 LEISURE.TIME STUDIES. 



internal forces and constitution of living beings, no one may 

 dogmatically assert. But our ignorance of the exact rela- 

 tions of these causes to outward conditions, will not militate 

 in any way against the recognition of the power of the latter 

 to effect change and alteration in living nature. In the 

 axolotl, the external influences of a land life are seen to 

 cause gills and tail fin to shrivel and ultimately to disappear. 

 In the young salamander, on the contrary, the vital process 

 of absorption must apparently be credited with the chief 

 share of the work of modification, and of causing gills and 

 other larval structures to become abortive. In the flat-fishes 

 a mechanical cause, namely, a tendency to lopsidedness, 

 presents us with the primary reason for the peculiar develop- 

 ment and position of the eyes. And we thus see in the 

 case of the axolotl, the mechanical beginnings of actions, 

 which in the flat-fishes and Alpine salamander have been 

 operating through long periods of time, and which, through 

 the agency of the law of likeness and heredity, have become 

 well-defined characters of the species. Admitting that varia- 

 tions may begin from without, that they are transmitted to 

 posterity, and that as time passes they may come, as we 

 have seen, to represent the " way of life," we are thus placed 

 in possession of rational ideas regarding the manner in which 

 cause and effect in one phase of nature are related. And 

 if it be urged that great are the mysteries which yet beset 

 the " ways of life," the knowledge we have obtained of even 

 a small part of the order of Nature may still be shown 

 to lead towards a fuller and wider comprehension of the 

 universe and its laws. We are now only studying the 

 alphabet of Nature. A little patience and we may be 

 able to say with Shakspeare's soothsayer : 



' ' In Nature's infinite book of secrecy 

 A little I can read." 



