_In the fifth place, it is an instructive fact on this subject that, as instruments have been improved, and observations have become more searching, the supposed cases of spontaneous generation have diminished_, until it is not pretended now that it takes place except in a very few tribes, and those the most obscure and difficult to observe of all living things. A hundred years ago, naturalists, and especially other men, might easily have been made to believe that many of the smaller insects had a casual origin. But long since, save in the matter of the acari, the entomological field has been abandoned by the advocates of the law hypothesis, and they have been driven from one tribe after another, till at length some of the obscure hiding-places of the entozoa and infusoria are now the only spots where the light is not too strong for the large-pupiled eyes of this hypothesis. Is not the presumption hence arising very strong that it will need only a little further improvement in instruments and care in observation to carry daylight into these recesses, and demonstrate the parentage and normal development of all organic beings? _Finally. The gross materialism inseparable from this hypothesis is a strong argument against it._ I am not aware that any one, except Oken, perhaps, has ever attempted to show that mind, as a spiritual essence, distinct from matter, has been created by natural laws; in other words, that there is in nature a power to produce mind. All such maintain that intellect is material, or, rather, the result of organization, the mere function of the brain, as are also life and instinct. Generally, also, they contend--and, indeed, consistency seems to require it--that the moral powers depend chiefly upon different developments of the brain; so that a disposition to do wrong results more from organization than from punishable mental obliquity; indeed, the worst of criminals are often, on this account, more to be pitied than blamed, and the physician is of more importance than the moralist and the divine for their reformation. Now, if this system of materialism is true, we ought to embrace it, without any fear of ultimate bad effects. But a philosopher will hesitate long before he adopts a system which thus seems to degrade man from his lofty standing as a spiritual, accountable, and immortal being, and makes his intellectual and moral powers dependent upon the structure of the brain, and, therefore, destined to perish with the material organization, with no hope of future existence, unless God chooses to recreate the man. Nay, if there be no distinct spirit in man, what evidence have we that there is one in Jehovah? A true philosopher, I say, will demand very strong evidence before he adopts any hypothesis that leads a logical mind to such conclusions; and I see not how the one under consideration can terminate in any thing else.