1 68 CHAPTERS ON EVOLUTION. 



building of the frame are marked out in plain and definite path- 

 ways by laws essentially independent of external conditions. True, 

 the development of the living form may be retarded by cold or 

 favoured by warmth, but these conditions leave unaffected the 

 course and direction in which it is destined to pass towards the form 

 and belongings of the parent which gave it birth. Stamped in- 

 effaceably on the pages of its life-history, the way of the animal or 

 plant towards maturity is written for it, not by it. Internal forces 

 and hidden but all-powerful laws of life direct its progress, and 

 ultimately evolve the perfect being from the shapeless germ, in 

 which its past as derived from its parents, and its future as depend- 

 ing in some degree at least upon itself, meet in strange and inconv 

 prehensible union. The development of a living being may be 

 further shown to be merely a part of the wondrous cycle in which 

 life appears to "direct its possessors. From the egg or germ, develop- 

 ment leads us to the perfect being. Next in order we consider its 

 adult or perfected history ; and in due time we may discover the 

 adult existence to merge into that of the immature state in the pro- 

 duction of germs, in the development of which its own life-history 

 will be duly repeated. The period of adult life in this view merely 

 intervenes betwixt one development and another, and serves to 

 connect those ever-recurring stages in the life-history of the race 

 which it is the.;province of development to chronicle and record. 



As a necessary item in the perfect understanding of animal and 

 plant history, it may readily be understood how important a place 

 development occupies in modern biology. Nor is the interest of the 

 study excelled by its importance. The mystery of life itself might 

 well be thought by the older physiologists to resolve itself into an 

 understanding of the fashion in which Nature moulded and formed 

 her varied offspring. The manner of development might be almost 

 expected to explain the mystery of being ; but the problem of life is 

 left as insoluble as before, after the course of development in even 

 the lowest grades of existence has been traced. The history of 

 development but environs the puzzles connected with life and its 

 nature. It leads us to the beginnings of life, it is true, but it leaves 

 these beginnings unaccounted for, and as mysterious as before. It 

 explains how this tissue or that, this organ or that, is fashioned and 

 formed ; and as we watch the formless substance giving birth to the 

 formed, the indefinite evolving the defined, we might well be tempted 

 to think that the " why " of nature was explained by the " how." 

 Yet the springs of life and vital action remain hidden as of yore, and 

 the exact origin of life is a mystery as insoluble as when the thoughts 

 of men were first directed to its elucidation. 



Apart, however, from the admission that the study of development 

 has not brought us nearer to the solution of the question, " What is 



