212 MAMMALIAN DESCENT. [Lect. IX. 



at the same plough, we see at once that they are 

 unequally yoked together. Sometimes we get a "cross " 

 between the two, but the two halves of such a nature 

 seldom amalgamate well ; yet there are some many- 

 sided minds that do wonders for us in harmonisino- even 

 these opposites. 



There is no room for despair. Our language has 

 Ijecome enriched, since some of us were young, with 

 many of the most valuable words that ever came in 

 to liel]) the development of thought. Our knowledge 

 has proceeded beyond the knowledge of our progenitors, 

 stretching, not merely to the utmost bounds of the 

 sea-girt hills, but to the bounds of the Cosmos, so 

 to sjDeak, which has no bounds ; and diving into the 

 depths of the warm life of living Being. This branch 

 of human knowledge has, I suj^pose, grown more 

 during this nineteenth century than in all the times 

 before ; back to Aristotle, back if you like to Moses, with 

 his clean and his unclean beasts. This is a new kino^dom 

 of science, this embryology, but you have to enter it 

 through a strait gate and a narrow way ; there is no 

 royal road to it. For here, unless a man stoops his 

 head, he will bruise it ; unless he enter silently he will 

 learn nothing. It is not nature revealed in a strong 

 wind, or an earthquake, or a fire ; it is the still small 

 voice of the growing cells he must train his ears to hear. 



" The spectacle afforded by the wonderful energies 

 prisoned within the compass of the microscopic hair of 



