102 



KNOWLEDGE. 



[June 1, 1893. 



narrow stalks. It is these hollow quills that make the 

 loud rattling sound heard when a porcupine is walking ; 

 and it appears to us not improbable that they may have 

 given rise to the old legend of the porcupine ejecting its 

 spines when attacked, as such hollow quills might well 

 have been thought to be receptacles for the ordinary 

 spines. Although their owner is unable to voluntarily eject 

 the latter, their pointed bases render them easily detached, 

 and leopards which habitually feed on porcupines are 

 found to be actually bristling with their quills. In attack- 

 ing its foes, the porcupine rushes at them backwards, and 



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Fie. 2.— The Common Hedgehog. 



thus gives full effect to its weapons. All the members of 

 the typical genus are characterized by their large size, 

 short tails, and highly convex skulls, and are confined to 

 the warmer regions of the Old World. The bush-tailed 

 porcupines (Atluruni) from West and Central Africa and 

 the Malayan region are, however, of much smaller size, 

 and also distinguished by their much longer tails, which 

 terminate in a brush of flattened spines, and are thus 

 evidently less specialized creatures. 



America is tenanted by a group of porcupines easily 

 distinguished from their Old World cousins by having 

 the soles of their feet covered with rough tubercles, instead 

 of being perfectly smooth, and also by their comparatively 

 short spines being mingled with a number of long hairs, 

 by which they may be partially concealed. The Canada 

 porcupine (ErHliiMii) differs from all the other American 

 species in ha\dng a short stumpy tail, and also in its non- 

 arboreal habits ; its spines being almost hidden by the 

 hairs. In parts of North America these porcupines are so 

 abundant as to be a positive nuisance, and an enterprising 

 engineer, with true American " cuteness,'' hit upon the 

 original idea of utilizing their bodies as fuel for his engine 

 -—apparently with tlie most satisfactory results. The 

 lighter built tree-porcupines (Si/tiet/wns), which are mainly 

 characteristic of the southern half of the American conti- 

 nent, are easily distinguished by their long tails, which, 

 as in so many South American mammals, are prehensile. 

 These porcupines are thoroughly arboreal in their habits, 

 and it is therefore easy to understand why their spines 

 are so much shorter than those of their terrestrial Old 

 World cousins, who have to rely solely on these weapons 

 for their protection. 



In addition to the members of the porcupine family, 

 there are several other groups of rodents which develop a 

 more or less complete coating of spines. Among the 

 most remarkable of these groups are the spiny mice 



(Acomijs) of Syria and Eastern Africa, one of which, when 

 it has its spines erected, is almost indistinguishable at the 

 first glance from a diminutive hedgehog. The spiny rat 

 of Celebes {Eihiiiothri.r) is another member of the mouse 

 family having the fur thickly intermingled with spines. 

 In a third rodent family [Dctodontida), nearly all the 

 members of which are South American, there is also a 

 genus (Krliinoin/s), taking its name from the number of 

 flattened spines mingled with the fur of the back charac- 

 terizing all its representatives. It will thus be obvious 

 that even in a single mammalian order we have several 

 instances where a protective coat of spines must have 

 been acquired quite independently. 



This independent origin is still more clearly indicated 

 when we come to the consideration of the hedgehog and its 

 allies, which bear precisely the same systematic relation- 

 ship to the porcupines as is presented by the true moles to 

 the mole- voles, as described in our last article. That is to 

 say, whereas the hedgehogs and true moles belong to the 

 insectivorous order, the porcupines and the mole-voles 

 are herbivorous rodents. In spite, then, of the general 

 similarity of appearance between a hedgehog and a porcu- 

 pine, or, still better, a spiny mouse, we shall find, as 

 already mentioned, that whereas the two latter have the 

 ordinary chisel-like rodent teeth, the former has several 

 narrow and somewhat irregularly-shaped teeth in the front 

 of the jaws, while its back teeth are crowned with 

 numerous sharp cusps, instead of having nearly smooth 

 grinding surfaces. Accordingly, from the purely systematic 

 point of view there is no justification for calling the 

 common hedgehog the " British porcupine " ; but, on the 

 other hand, if we allow similarities in external appearance to 

 be our guide in nomenclature, there are just as good grounds 

 for applying the latter title to the hedgehog as there are 

 for giving the names of golden or Cape mole, sand-mole, 

 mole-vole and marsupial mole to tour of the creatures 

 noticed in our last month's article. Our ancestors, to 

 whom the hedgehog was commonly known as the 

 " urchin," went, however, a step further than this, and, 

 from the resemblance of its spines to those of the mammal, 

 gave the name of sea-urchin to the Echinux, a title which 

 has stuck to it ever since. Systematic zoologists need 

 not then wax so wroth as we have known them 

 do when the name of " British porcupine " is applied 

 to the urchin, seeing that the analogies of nomen- 

 clature are sufficient to justify its use. As the sea- 

 urchins come most distinctly under the title of spiny 

 animals, it may be mentioned here that, although the 

 spines of the common British species are not unlike those 

 of the hedgehog, yet their structure is totally different. 

 Thus, whereas the spines of the mammal are of a horny 

 nature, those of the invertebrate owe their solidity to the 

 presence of carbonate of lime, and always break with the 

 characteristic oblique fracture of the mineral calcite. More- 

 over, whereas the spines of the hedgehog are implanted in 

 its skin, those of the sea-urchin are entirely external, being 

 movably attached by their hollow bases to knobs on the 

 surface of the shell or "test." Whether our worthy 

 ancestors believed that the land and sea-urchins were con- 

 nected by ties similar to those which in their estimation 

 affiliated barnacle-geese to barnacles, or how the name 

 "urchin" came also to indicate a child, we are quite 

 unaware. 



In place of terminating in sharp points, by which they 

 are but loosely attached to the skin, like those of the por- 

 cupine, the spines of the hedgehog termmate inferiorly in 

 small knobs, which are placed beneath the skin, and may 

 thus be compared to pins stuck through a piece of soft 

 leather. Beneath the skin lies a layer of muscle known as 



