Spencer and Darwin occasionally see this difficulty, though they habitually neglect it in their reasonings. Spencer even tries to turn one part of it to account as follows:-- "Suppose the head of a mammal to become very much more weighty--what must be the indirect results? The muscles of the neck are put to greater exertions; and the vertebræ have to bear additional tensions and pressures caused both by the increased weight of the head and the stronger contraction of muscles that support and move the head." He goes on to say that the processes of the vertebrae will have augmented strains put upon them, the thoracic region and fore limbs will have to be enlarged, and even the hind limbs may require modification to facilitate locomotion. He concludes: "Any one who compares the outline of the bison with that of its congener, the ox, will clearly see how profoundly a heavier head affects the entire osseous and muscular system." We need not stop to mention the usual inaccuracies as to facts in this paragraph, as, for example, the support of the head being attributed to muscles alone, without reference to the strong elastic ligament of the neck. We may first notice the assumption that an animal can acquire a head "very much more weighty" then that which it had before, a very improbable supposition, whether as a monstrous birth Dr as an effect of external conditions after birth. But suppose this to have occurred, and what is even less likely, that the very much heavier head is an advantage in some way, what guarantee can evolution give us that the number of other modifications required would take place simultaneously with this acquisition! It would be easy to show that this would depend on the concurrence of hundreds of other conditions within and without the animal, all of which must co-operate to produce the desired effect, if indeed they could produce this effect even by their conjoint action, a power which the writer, it will be observed, quietly assumes, as well as the probability of the initial change in the head. Finally, the naivete with which it is assumed that the bison and the ox are examples of such an evolution, would be refreshing in these artificial days, if instances of it did not occur in almost every page of the writings of evolutionists. It would only weary the reader to follow evolution any further into details, especially as my object in this chapter is to show that generally, and as a theory of nature and of man, it has no good foundation; but we should not leave the subject without noting precisely the derivation of man according to this theory; and for this purpose I may quote Darwin's summary of his conclusions on the subject.[BC] [BC] "Descent of Man," part ii., ch. 21.