of the ferpent tribe, is that of cafting their fkins at cer- 

 tain periods, and appearing in a ftate of fuperior beau- 

 ty in point of colour than before* This is one of the 

 principal caufes of that difficulty which obtains amongft 

 Naturalifts of determining the fpecies \ fince one and 

 the fame animal may vary extremely in colour at diffe- 

 rent feafons, and therefore be miftaken for a different 

 fpecies. Linnaeus gives a very good and probable rea- 

 fon for this, viz. 'That fince the Author of Nature has 

 c armed many of the ferpent tribe with a dreadful poi- 

 4 fon, He has ordained that all Ihould caft their fkins, in 

 f order to infpire a neceflary univerfal caution and fuf- 

 'picion of the whole tribe.* 



