Half of this I'm keeping, but the second half proves irrelevant, so I will preserve it here instead, to enable ruthless manuscript-cutting...
The first quotation is Charles Bonnet writing to the Italian physiologist Lazzaro Spallanzani, in the version published in the collection of Spallanzani’s writings that appeared in English in 1784:
You are not in possession of a sure and easy way of ascertaining what species can procreate together; and the experiments you propose attempting next spring, by putting your voluptuous spaniel in the company of cats and rabbits, promise not so far as those which you will make, by introducing the semen of this spaniel into the uterus of a doe-rabbit and a she-cat, and on the other hand, by introducing the semen of the male rabbit and cat into the uterus of a bitch. You hold in your hand a precious clue, which will guide you to the most important and unexpected discoveries. I know not, whether what you have now discovered, may not one day be applied in the human species to purposes we little think of, and of which the consequences will not be trivial. You conceive my meaning: however that may be, I consider the mystery of fecundation as nearly cleared up. What remains principally to be discovered, is the formation of the mule, and what occasions the different marks of resemblance between children and their parents.I am sorry to say that Spallanzani did not succeed in bringing about the dog-cat hybrid he hoped for, but he retained his conviction that the experiments themselves were worthwhile:
Should any one of my injections prove prolific, and should the young partake, both in form and manners, of the female which conceived them, and the male that furnished the seed, I fancied, that the most singular mules, and such as had never been before seen, would now be produced. With respect to manners, two most opposite natures would be kneaded together and be confounded; the one, that of an animal susceptible of education, full of courage, abilities, and sentiment, all ardour, all affection, all obedience to his master; the other, that of an animal in internal qualities, far inferior, by instinct intractable, abhorring all subjection, faithless to its owner, affectionate only through interest, and born with an irreconcileable enmity to the former. Nor would the nature of these two animals engrafted together, be less different in a physical point of view[.]Bonus link: the great eighteenth-century naturalist Buffon on the cat:
The cat is an unfaithful domestic, and kept only from the necessity we find of opposing him to other domestics still more incommodious, and which cannot be hunted; for we value not those people, who, being fond of all brutes, foolishly keep cats for their amusement. Though these animals, when young, are frolicksome and beautiful, they possess, at the same time, an innate malice, and perverse disposition, which increase as they grow up, and which education learns them to conceal, but not to subdue. From determined robbers, the best education can only convert them into flattering thieves; for they have the same address, subtlety, and desire of plunder. Like thieves, they know how to conceal their steps and their designs, to watch opportunities, to catch the proper moment for laying hold of their prey, to fly from punishment, and to remain at a distance till solicited to return. They easily assume the habits of society, but never acquire its manners; for they have only the appearance of attachment or friendship. This disingenuity of character is betrayed by the obliquity of their movements, and the duplicity of their eyes. They never look their best benefactor in the face; but, either from distrust or falseness, they approach him by windings, in order to procure caresses, in which they have no other pleasure than what arises from flattering those who bestow them.