PRE-DETERMINATION IN NATURE 339 



altogether soft and spongy skeletons in these old times, their 

 remains do not seem to have been preserved. 



Here, it will be observed, are a great variety of vital and 

 mechanical contrivances devised in the very early history of the 

 earth, settled for all time, and handed down without improve- 

 ment, and with little change, to our later day. They are indeed 

 vastly more wonderful than the above general account can show ; 

 for to go into the details of structure of any one of the species 

 would develop a multitude of minor complexities and niceties 

 which no one not specially a student of these animals could 

 appreciate. 



These are not solitary cases. The student of fossils meets 

 with them at every turn ; and if he possesses the taste and 

 imagination of a true naturalist, cannot fail to be impressed with 

 them. 



To turn to a later but very ancient period, what can be more 

 astonishing than those first air-breathing vertebrates of the 

 Coal formation referred to in a previous chapter, with all their 

 special arrangements for an aerial habitat ? I have mentioned 

 their footprints, and when we see the quarrymen split open a 

 slab of sandstone and expose a series of great plantigrade tracks, 

 not unlike those of a human foot, with the five toes well deve- 

 loped, we are almost as much astonished as Crusoe was when 

 he saw the footprints on the sand. Crusoe inferred the presence 

 of another man in his island ; we infer the earliest appearance 

 of an air-breathing vertebrate and the pre-human determination 

 of the form and number of parts of the human foot and hand, 

 to appear in the world long ages afterward. We see also that 

 already that decimal system of notation which we have founded 

 on the counting of our ten fingers was settled in the framework 

 of most unmathematical Batrachians. It has approved itself ever 

 since as the typical and most perfect number of parts for such 

 organs. 



If sceptically inclined, we may ask. Why five rather than 



