Among Prerogative Instances I will put in the ninth place Bordering Instances, which I also call Participles. They are those which exhibit species of bodies that seem to be composed of two species, or to be rudiments between one species and another. These instances might with propriety be reckoned among singular or heteroclite instances, for in the whole extent of nature they are of rare and extraordinary occurrence. But nevertheless for their worth's sake they should be ranked and treated separately, for they are of excellent use in indicating the composition and structure of things, and suggesting the causes of the number and quality of the ordinary species in the universe, and carrying on the understanding from that which is to that which may be.
Examples of these are: moss, which holds a place between putrescence and a plant; some comets, between stars and fiery meteors; flying fish, between birds and fish; bats, between birds and quadrupeds; also the ape, between man and beast —
Simia quam similis turpissima bestia nobis;
likewise the biformed births of animals, mixed of different species, and the like.
'Simia quam similis turpissima bestia nobis' is from the Latin poet Ennius, but is known only because it is quoted by Cicero (De Natura Deorum, I, XXXV):
But how thoroughly beside the point the argument from resemblance, with which you are so mightily charmed, is in itself. Is not a dog like a wolf? And, as Ennius says:—
How like to us is the degraded ape!
Yet the character in both cases is different.
It means, "How similar the ape (simian), that very ugly beast, is to us!" We find what seems to be an allusion to it in Arnobius's Adversus Gentes, Book III:
But you will, perhaps, say that the gods have indeed other forms, and that you have given the appearance of men to them merely by way of honour, and for form's sake 50 which is much more insulting than to have fallen into any error through ignorance. For if you confessed that you had ascribed to the divine forms that which you had supposed and believed, your error, originating in prejudice, would not be so blameable. But now, when you believe one thing and fashion another, you both dishonour those to whom yon ascribe that which you confess does not belong to them, and show your impiety in adoring that which you fashion, not that which you think really is, and which is in very truth. If asses, dogs, pigs, had any human wisdom and skill in contrivance, and wished to do us honour also by some kind of worship, and to show respect by dedicating statues to us, with what rage would they inflame us, what a tempest of passion would they excite, if they determined that our images should bear and assume the fashion of their own bodies? How would they, I repeat, fill us with rage, and rouse our passions, if the founder of Rome, Romulus, were to be set up with an ass's face, the revered Pompilius with that of a dog, if under the image of a pig were written Cato's or Marcus Cicero's name? So, then, do you think that your stupidity is not laughed at by your deities, if they laugh at all? or, since you believe that they may be enraged, do you think that they are not roused, maddened to fury, and that they do not wish to be revenged for so great wrongs and insults, and to hurl on you the punishments usually dictated by chagrin, and devised by bitter hatred? How much better it had been to give to them the forms of elephants, panthers, or tigers, bulls, and horses! For what is there beautiful in man,-what, I pray you, worthy of admiration, or comely,-unless that which, some poet has maintained, he possesses in common with the ape?
Montaigne also uses the saying in his "Apology for Raymond Sebonde" (Essays II, XII):
Et quelles qualitez de nostre corporelle constitution en Platon et en Cicero ne peuvent servir à mille sortes de bestes ?
Celles qui nous retirent le plus, ce sont les plus laides, et les plus abjectes de toute la bande; car pour l'apparence exterieure et forme du visage, ce sont les magots :
Simia quam similis, turpissima bestia, nobis !
pour le dedans et parties vitales, c'est le pourceau. Certes quand j'imagine l'homme tout nud (ouy en ce sexe qui semble avoir plus de part à la beauté) ses tares, sa subjection naturelle, et ses imperfections, je trouve que nous avons eu plus de raison que nul autre animal, de nous couvrir. Nous avons esté excusables d'emprunter ceux que nature avoit favorisé en cela plus que nous, pour nous parer de leur beauté, et nous cacher soubs leur despouille, de laine, plume, poil, soye.
(For an English translation, albeit an old one, see here.)