III. The Ganoids and other fishes like the Lepidosiren. These, we are told, "must have been developed" from the preceding (II). The Ganoids, it is said, were fishes covered with peculiar enameled bony scales. Most of them are said to be extinct, but enough is known about them to lay the foundation for their "probable" development from the first fishes that are supposed to have been derived from the aquatic worm (I). There is a reason for arguing the existence of these first fishes as a true fish with the power of locomotion, because the next ascending group of animals is to be the Amphibians. In a fish, the swim-bladder is an important organ; and it is an organ that plays an important part in the Darwinian theory, furnishing, it is claimed, a very remarkable illustration that an organ constructed originally for one purpose, flotation, may be converted into one for a widely different purpose, namely, respiration. As the Amphibians, which as a distinct group were to come next after the fishes in the order of development, must be furnished with a true air-breathing lung, their progenitors, which inhabited the water only, must be provided with an organ that would undergo, by transitional gradations, conversion into a lung. But what is to be chiefly noted here is that it is admitted that the prototype, which was furnished with a swim-bladder, was "an ancient and unknown prototype"; and it is a mere inference that the true lungs of vertebrate animals are the swim-bladder of a fish so converted, by ordinary generation, from the unknown prototype because the swim-bladder is "homologous or 'ideally similar' in position and structure with the lungs of the higher vertebrate animals."[37] One might ask here without presumption, why the Omnipotent God should not have created in the vertebrate animals a lung for respiration, as well as have created or permitted the formation of a swim-bladder in a fish; and looking to the probabilities of the case, it is altogether too strong for the learned naturalist to assert that "there is no reason to doubt that the swim-bladder has actually been converted into lungs or an organ used exclusively for respiration"; especially as we are furnished with nothing but speculation to show the intermediate and transitionary modifications between the swim-bladder and the lung. While we may not assume "that the Creator works by intellectual powers like those of man," in all respects, it is surely not presumptuous to suppose that an Omnipotent and All-wise Being works by powers that are competent to produce anything that in his infinite purposes he may see fit specially to create.