(IK, A TKEATISK ON PILE. 161 



do really, in the physiological as well as in the popular sense, propagate the : r kind, trans- 

 mitting to their descendants all the distinctions of kind, (down to the most special and 

 lowest kind,) which they themselves possess." Now surely one of " the distinctions of 

 kind," of the hairy Sheep is, " to produce hair" and one of " the distinctions of kind" of 

 the woolly Sheep is, " to produce wool.'" 



In like manner, Agassis, (in Prin. of Zool. 43,) says, "the constancy of species is a 

 phenomenon depending on immaterial nature. Animals (and plants also) produce their 

 kind, generation after generation. We shall hereafter show, that all animals may I e 

 traced back, in the embryo, to a mere point upon the yolk of the egg, bearing no resem- 

 blance whatsoever to the future animal. But even here (he adds) an immaterial principle, 

 which no external influence can prevent, or modify, is present, and determines its future 

 form, so that the egg of the hen can produce nothing but the chicken, and the egg of the 

 codfish can produce only the cod. It may, therefore, be said with troth, that the chicken 

 and the cod existed in the egg before their formation." Now, although this learned author 

 has given us examples drawn from two classes of animals, viz : the chicken and the fish. 

 it is fair to presume that he meant his observations to apply to animals of different species 

 but of the same class and order, and therefore, that the hair of the hairy Sheep and the 

 wool of the woolly Sheep depends upon an immaterial principle, which no external influ- 

 ence can prevent or modify." The question of species, is, therefore, one of fact, and Dr. 

 Morton was right when he said that "all circumstances which tend to establish analogies 

 are proper and necessary for the determination." We admit, that where common parent- 

 age can be traced, with certainty, that it constitutes the best evidence that the nature of 

 the case admits; but he who would reject secondary evidence, when primary cannot be 

 obtained, would place himself in the position of one who would shut his eyes to all other 

 light, because he cannot always bask in the rays of the sun. 



Between animals of the same species nature throws no impediment whatever to free 

 sexual intercourse, and the progeny form a permanent, self-supporting race of animals 

 which inherit equally the properties of both parents. But with animals of dijferent species 

 there is a natural abhorrence to amalgamate, which sometimes cannot be overcome at all ; 

 and which at others exhibits itself in various ways and in various degrees ; and the progeny 

 is always incapable of securing a permanent and self-supporting race, in the proper sense 

 of those terms. This is a most valuable rule for the determination of species, when 

 properly understood and correctly applied ; but from inattention and inadvertence, it has 

 been converted into a fruitful hot-bed of error, as will be hereafter shown in the proper 

 place. 



The common Cow and the Buffalo have, we are told, a natural antipathy to each other. 

 Such is the fixed aversion formed between these creatures, (as we are informed by Gold- 

 smith,) that the Cow refuses to breed with the European Buffalo, which she nearly 

 resembles. 



Wild Asses, (as we are told by the same beautiful author,) live in herds, but they will 

 not allow a Horse to come among them ; if, perchance, one strays into the boundary of 

 their grazing ground, they fall upon him, and without even giving him time to reireat, 

 they kick and bite him until he is left exhausted on the spot. 



