ago PHILOSOPHICAL TRANSACTIONS. [aNNO I676. 



cause. For, say they, that which renders mules sterile is not the defect of any 

 of the organs necessary to generation, since the difference which may be found 

 in the conformation of the matrix of a mare and of that of a she ass cannot, as 

 some pretend, be a ground of this cause of sterility; the ;mare, in which some- 

 thing is deficient that is found in the she ass, not being destitute of any of the 

 parts absolutely necessary to engender, because it does engender; and the dif- 

 ference of the organs being not the cause of barrenness, forasmuch as the dif- 

 ference of organs which is between the species of horses and asses, hinders not 

 the breeding of mules, which issue from the mixture of those two species. 

 Whence Aristotle, following Empedocles, imputes this defect only to the tem- 

 perament of those animals, whose parts have contracted a hardness that renders 

 them incapable to contribute to a new mixture; so that if it be true that most 

 of the animals which are born of the mixture of two kinds, are notwithstand- 

 ing fruitful, they are inclined to believe that the conformation of this chat pard 

 was peculiar and accidental, and that the defect of the parts which it wanted, 

 and which made it incapable of engendering, proceeded not from that mixture 

 of species, which by changing the conformation of the parts cannot so spoil the 

 same as to render it unfit for the functions, and is yet less capable to make a 

 mutilation; but may more easily cause some vice in the temperament, which is 

 a very natural sequel of mixture ; and lastly, that it is probable, that if the mule 

 be the only animal which the confusion of species renders sterile, there is some- 

 thing particular in those animals that have engendered it, which is not found in 

 others, and that is perhaps, as Aristotle thinks, the hardness of the matrix in 

 mares and asses, which like an earth is rendered sterile by driness; whereas 

 that reason has no place in leopards, foxes, and others, which are animals fe- 

 cund enough to transmit to their offspring the strong dispositions they have for 

 generation, notwithstanding the resistance which the mixture of different species 

 may bring. [Why some hybridous animals are prolific, and the generality of 

 them not, is a matter wholly inexplicable.] 



The third is the sea fox,* in whose stomach they found a branch of the sea 

 herb varec, and a fish of five inches long, without its head, scales, skin, and 

 bowels, all having been consumed, except the muscular flesh, which was yet en- 

 tire. And as to its guts, they observe, that the upper part of them had a peculiar 

 structure, and instead of the ordinary circumvolutions of guts, the cavity of 

 these was distinguished by many transverse separations, composed of the mem- 

 branes of the intestine turned inwards, which separations were half an inch 

 distant from one another, and turned helically, like a snail shell ; which may 



* A species of shark. Squalus vulpes. Linn. 



