June 1, 1898.] 



KNOWLEDGE. 



101 



^^ AN ILLUSTRATED '^^ 



MAGAZINE OF SCIENCE 



SIMPLY WORDED— EXACTLY DESCRIBED 



LONDON: JUNE 1, 1893. 



CONTENTS. 



PAGE 



Spiny Animals. By R. Ltdekkeb, B.A.Cantab 101 



Caterpillars' Dwellings— TTT. By E. A. Butlee 104 



The Oldest Book in the World. V,\ J. II. ItiTCHixEi!, 



F.R.A.S 106 



Science Notes 107 



What is a Star Cluster? By A. C. Eantard 109 



Notices of Books Ill 



Letters:— W. H. S. Moxck ; W. T. Lyn^ ; Thos. Blashill 112 

 On the Distribution of the Stars in Space. By Prof. 



J. C. Kapteyx 114 



The Face of the Sky for June. By Hbebeet Sadleb, 



F.R.A.S. 118 



Chesa Column. By C. D. Locogk, B.A.Osod 119 



SPINY ANIMALS. 



By E. Lydekker, B.A. Cantab. 



IN our article on " Moles and their Like," published 

 in the May number of Knowledge, it was shown 

 how the adaptation to the necessities of a particular 

 mode of life has produced a marked general external 

 resemblance in certain burrowing mammals belonging 

 to several more or less completely distinct groups. We 

 now propose to point out the resemblances existing between 

 certain other members of the same class of animals, owing 

 to the assumption of a protective coat of spines. Although' 

 this resemblance is in some instances not so striking as 

 among the creatures noticed in our previous article, yet it 

 is quite sufficient to have obscured in popular estimation 

 the real affinities of some of the spine-bearing mammals, 

 as it is by no means uncommon to hear the hedgehog 

 spoken of as the " British porcupine," while certain 

 Madagascar spiny mammals are frequently alluded to as 

 hedgehogs, and the Australian echidna is commonly 

 alluded to as a porcupine. Moreover, the names " sea 

 urchins " and " sea hedgehogs," applied to animals 

 belonging to totally different classes, shows the important 

 estimation held by spines in popular zoology. It is almost 

 superfluous to add that the acquisition of the coat of spines 

 in all the mammals here alluded to is solely for the pur- 

 pose of protection ; and how sufficient is this protection in 

 most cases, is evident to all who have seen how the 

 hedgehog, when rolled up, sets most dogs at defiance. 

 Still, however, this panoply is by no means invariably 



proof against all attacks, as it appears to bo well ascer- 

 tained that leopards and pumas will kill and eat porcupines 

 witbout the slightest hesitation, and with a total disregard 

 of their formidable spines, which may be found sticking in 

 all parts of the bodies of the devourers. As wo found to be 

 the case with the mole-like mammals, all the spiny mammals 

 belong to the lower orders of the class, their several represen- 

 tatives beingdistributedamong the insectivores, rodents, and 

 egg-laying groups, and the majority pertaining to the two 

 former of these. In fact, in this respect an exact 

 parallelism may be drawn between the mole-like and 

 the spiny mammals, each assemblage having several 

 representatives among the insectivores and rodents, while 

 the former has a solitary marsupial type, and the latter 

 two members among the egg-laying mammals. Some 

 of these spiny mammals, such as the true porcupines 

 and the echidnas, are burrowing creatures, and thus have 

 a double means of defence against their enemies ; others, 

 however, like the hedgehog, rely on their power of rolling 

 themselves up into a ball, and thus presenting a rhevmix- 

 df-fn'M' on all sides. Some again, like the tree-porcupines, 

 are more or less completely arboreal in their habits ; and 

 the whole of them, like the mole-like mammals, show how 

 urgent has been the need for the lowly-organized rodents, 

 insectivores, and egg-laying mammals to acquire some 

 special means of protection in order to be able to hold 

 their own among the higher forms. As all our readers 

 are doubtless aware, in mammals spines are nothing more 

 than specially modified hairs, and in a porcupine the 

 transition from a spine to an ordinary hair can be easily 

 seen. There are many rodents in which a certain number 

 of scattered spines are mingled with the fur of the back, 

 but our remarks will be confined in the main to the 

 forms in which the spines predominate sufficiently to 

 render them the most striking feature in the external 

 appearance of their possessors. 



Commencing with the rodents, our first representatives 

 of the spiny mammals will be the true porcupines (Hi/stri.r), 

 which are such well-known creatures as to require but 

 brief description. These animals conform, of course, to 

 the ordinary rodent type in having a single pair of large 



Fig. 1. — The Common Porcupine.* 



chisel-like incisors in each jaw ; and their spines are most 

 developed on the middle line of the head and back, 

 the hinder part of the body, and on the short tail. 

 Whereas, however, those on the body are solid throughout 

 and pointed at each end, the spines at the extremity of the 

 short tail are in the form of hollow quills inserted by 



* We are indebted to Messrs. F. Warne and Co. fox' the loan of 

 the three figures n-ith which this article is illustrated. 



