258 THE BEGINNINGS OF LIFE. 



comparatively higher forms of life^ we can, at all events, 

 see our way to expect that such diverse combinations 

 of matter and motion might result in an almost endless 

 diversity of organic form. But we should expect that 

 given sets of conditions acting upon essentially similar 

 organic materials would give rise, on different occasions, 

 to organisms more or less similar. So that we can 

 only conclude that constantly recurring forms are to 

 be looked upon as the result of certain original com- 

 binations of matter and motion, and subsequent inter- 

 actions, more or less similar in kind, between such 

 initial combinations and their environments. The 

 forms of elementary organisms ought to have a generic 

 constancy and correspondence with the conditions 

 under which they have been evolved, similar to that 

 which we find in the case of crystals — though of course 

 with a much wider range of possible variation. And 

 as slight variations in one or other of the factors 

 may be continually anticipated, rather than absolute 

 similarity, we should be led to expect that organisms 

 so evolved would be liable to present many variations 

 in form — that, though exhibiting characters generally 

 similar, they should nevertheless be found to differ 

 continually in matters of minor detail. 



Animals or plants that have been derived from simi- 

 lar parents which multiply sexually, possess an inherited 

 tendency to develop in given directions, and thus the 

 type or pattern is more likely to be perpetuated. But 

 Infusoria and Fungus-germs evolved from a pellicle — 



