8 



evolution is, as well as to tlie elucidation of natural selec- 

 tion as a most potent factor in evolution, we are indebted 

 to Charles Darwin. Whereas formerly we saw through a 

 glass darkly, we now see clearly face to face — 



" Eye to eye we look 



On knowledge — in our hand 

 Is nature, like an open book." 



What is our evidence ? There are many lines of argument 

 leading to one conclusion, and which I shall venture, if your 

 patience will permit, to consider with you seriatim. 



Let us first take the argument from the developmejit of the 

 individual, or Emhryology. Von Baer was the first to point 

 out that, in the vital series, differentiation takes place from 

 the general to the special. "WTiat is true of any series, 

 historically and structurally considered, is also true of the 

 development of any individual of that series. 



We will at once take the crucial test — man himself — and I 

 will ask you, when you have heard the evidence, to decide 

 whether, if the individual man rapidly passes in his develop- 

 ment through a series of changes leading from the simplest 

 to the most complex form of life, and these changes are 

 crowded into so inconsiderable a space of time, we need be 

 very surprised to learn that the race has attained its high 

 organization in the eeons of geological time. A human 

 being, as well as all animal and vegetable forms, first 

 appears as a simple protoplasmic cell — a speck of albu- 

 minous jelly, like a protococcus, or a torula, or any other of 

 the lowliest forms of vegetable life. This cell then under- 

 goes yelk segmentation and develops into two layers of 

 cells, while it also becomes grooved, so as to resemble a 

 hydra — one of the jelly-fish tribe, which is also depressed 

 and is differentiated into a double layer of cells : next the 

 free ends of the groove unite and enclose an alimentary 

 canal ; the essential structure of the organism at this period 

 being decidedly and strictly comparable to very low forms 

 indeed of animal life. Meanwhile another depression 

 appears on the opposite side to the first, the edges of which 

 unite, while in their cavity the central nervous system is 

 developed. The embryo now resembles the amphioxus 

 of the sea-shore. A vertebral column now appears between 

 the two great body cavities ; but to determine whether the 

 organism will bec-ome a perch, a crow, a dog, or a man, 

 would not at this stage be a matter of extreme simplicity. 



