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zones. The number five disappears in the Radiata, to reappear 

 in the vertebrata. With all the various arrangements for 

 swimming, running, and climbing, the number of claws on a bird's 

 foot varies considerably, and four is a more common number than 

 five, which, in fact, is only found in domesticated varieties, but 

 there can be no question as to five being the type number of 

 fingers and toes in the mammilea. In many cases, as in the 

 Hoofed Animals, several are wanting, but the number is never 

 exceeded, and may be looked upon as constant. Number Six is 

 common enough, but is generally a mere double of three. It is, 

 however, noticeable as being the sign of that hexagonal form 

 which is found in the honeycomb, the cellular tissue of some 

 plants, the crystals of snow, &c. It is fashionable to account for 

 this form by the mutual pressure of circles, but it is in many cases 

 deliberately chosen by animals who build under circumstances 

 where external pressure is impossible. The Number Six is also 

 remarkable as being that of an insect's legs, and when we consider 

 the great difference between the animals forming their class, we 

 are astonished to find them connected by so uniform a link, and 

 the more so when we remember that only four wings accompany 

 them, the number being made good in the Diptera by the presence 

 of " poisers. " Seven is remarkable as being the constant number 

 of cervical vertebrae in the Mammalia, the two exceptions 

 being only apparent. When we compare the short neck of the 

 rhale with the long one of the giraffe, and reflect that each is 

 composed of the same number of bones, we feel that Nature has 

 »one apparently out of her way to preserve what seems to us 

 Ian unimportant point of likeness between animals differing in 

 [in almost those points which we should consider essential. Eight 

 id Ten are numbers representing the limbs of the Arachnida and 

 Crustacea respectively, and they are suggestive. In the Centipede, 

 l«omposed of a large mumber of somites, each with its two legs, its 

 [haemal and digestive apparatus, and its central ganglion, we have 

 [a mere line of connected parts, following a head, which, as 

 composed of several rings, indicates a centralization of vital power. 



