OR, A TREATISE ON PILE. 161 
do really, in the phystological 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 Zodl. 43,) says, “the constancy of species is a 
phenomenon depending on zmmaterial nature. Animals (and plants also) produce theer 
kind, generation after generation. We shall hereafter show, that all animals may le 
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 truth, 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 speczes 
but of the same class and order, and therefore, that the hazr 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 mwhatever 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 different 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 bim time to retreat, 
they kick and bite him until he is left exhausted on the spot 
