A subject of no small importance in its religious bearings has recently excited a good deal of sharp discussion in this country. I refer to the questions of the specific unity and unity of origin of the human race. To a person who has never studied the subject, it seems a matter easy to settle; yet, in fact, it demands extensive research even to understand. And we have seen one of the most accomplished zoologists and anatomists of the present age take ground on these points in opposition to the almost universal opinion. The result has been that not a few talented replies to his arguments have appeared, mostly, I believe, from ministers. I have not seen them all. But in respect to those which I have read it has seemed to me, without having the least sympathy with the views of Professor Agassiz, that the authors have not the most remote conception of the principal arguments on which he relies, derived from zoology and comparative anatomy; nor do I believe that they can understand and appreciate them until they have studied those sciences.[1] Although I fear that theologians are not aware of the fact, yet probably the doctrines of materialism are more widely embraced at this day than almost any other religious error. But in which of our schools, save the medical, is there any instruction given in physiology and zoology, that will prepare a man to make the least headway against such delusions? The arguments by which materialism is defended are among the most subtle in the whole range of theology and natural science; and without a knowledge of the latter they can neither be appreciated nor refuted. The mere metaphysical abstractions by which they are usually met excite only the contempt of the acute physiologist who is a materialist. I might refer, in this connection, to the whole subject of pantheism, in its chameleon forms. The rhapsodies of spiritual pantheism must, indeed, be met by metaphysics equally transcendental. But, after all, it is from biology that the pantheist derives his choicest weapons. He appeals, also, to astronomy, zoology, and geology; nor is it the superficial naturalist that can show how hollow is the foundation on which he rests.