THE EVOLUT ION- HYPOTHESIS. 349 



by minute, the ellipse becomes first perceptibly eccentric, then 

 manifestly so, and by and by acquires so immensely elongated 

 a form, as to bear no recognizable resemblance to a circle. 

 By continuing this process, the ellipse changes insensibly into 

 a parabola. On still further diminishing the angle, the para 

 bola becomes an hyperbola. And finally, if the cone bo 

 made gradually more obtuse, the hyperbola passes into a 

 straight line, as the angle of the cone approaches 180. Now 

 here we have five different species of line circle, ellipse, 

 parabola, hyperbola, and straight line each having its pecu 

 liar properties and its separate equation, and the first and 

 last of which are quite opposite in nature, connected together 

 as members of one series, all producible by a single process 

 of insensible modification. 



But the experiences which most clearly illustrate to us 

 the process of general evolution, are our experiences of 

 special evolution, repeated in every plant and animal. Each 

 organism exhibits, within a short space of time, a series 

 of changes which, when supposed to occupy a period inde 

 finitely great, and to go on in various ways instead of one 

 way, give us a tolerably clear conception of organic evo 

 lution in general. In an individual development, we have 

 compressed into a comparatively infinitesimal space, a series 

 of metamorphoses equally vast with those which the hypo 

 thesis of evolution assumes to have taken place during those 

 immeasurable epochs that the Earth s crust tells us of. A 

 tree differs from a seed immeasurably in every respect 

 in bulk, in structure, in colour, in form, in specific gravity, 

 in chemical composition : differs so greatly that no visible 

 resemblance of any kind can be pointed out between them. 

 Yet is the one changed in the course of a few years into the 

 other : changed so gradually, that at no moment can it be 

 said Now the seed ceases to be, and the tree exists. What 

 can be more widely contrasted than a newly-born child and 

 the small, semi- transparent, gelatinous spherule constituting 

 the human ovum ? The infant is so complex in structure 



