27 



is open to question whether the natural formation of a crystal ia 

 not very similar, and at any rate it is impossible to group solid 

 forms without a geometry of three dimensions — length, breadth ,- 

 and thickness. 



The Number Four is a very important one in Nature. 

 Amongst animals it suggests the vertebrata. That large class, 

 differing so entii-ely from all other animals in their bodily 

 and /'shall we say) mental characteristics, are universally distin- 

 guished by four limbs, expressed or understood, as Euclid says. 

 In the Land Mammalia, and the lizards, this fact is readily recog- 

 nised, but becomes somewhat obscure when we find them changed 

 into wings in the birds, flappers in the turtle, and fins in the fish, 

 or suppressed altogether as in most snakes. Still a consecutive 

 observation of vertebrate skeletons will convince the student tha 

 the vertebrata are essentially four-limbed animals. Bacon's 

 observation on snakes comes in well here. It is true that the 

 gliding snake does form its flexible body into four curves, and at 

 the alternate junctions of these curves, just, in fact, where our 

 instinctive habit would place the shoulders and loins, there are 

 two strong positions which take hold of the ground with more 

 force than any other part. If a long snake be wounded by a blow 

 from a cane, it is from one of these places that he raises himself, 

 and if he be held in front of a scorching fire these two points of 

 his body at once project themselves, giving rise to the wide- 

 spread belief of bushmen and savages, that snakes have short legs 

 beneath their skin. This number seems nearly peculiar to the 

 vertebrata, as I find only one other instance of it, namely, in the 

 Medusje, or jelly fish. These beautiful organisms are marked 

 with four radiating canals, which were long looked upon as a 

 mark of distinction between the Discophora, or naked-eyed 

 Medusae, and the gonophores of the Campanularida. It is how- 

 ever found in both, and in the " hidden eyed " Medusce, the 

 cruciform mark is also very evident. The Number Four is no less 

 important in the Vegetable Kingdom, where it furnishes a type for 

 the two widely differing orders, Labiatae and Crucifera\ In the 



