OF ORGANIC NATURE. 19 



every part becoming gradually and slowly fashioned, as 

 if there were an artificer at work in each of these complex 

 structures that I have mentioned. This embryo, as it 

 is called, then passes into other conditions. I should tell 

 you that there is a time when the embryos of neither 

 dog, nor horse, nor porpoise, nor monkey, nor man, can 

 be distinguished by any essential feature one from the 

 other ; there is a time when they each and all of them 

 resemble this one of the Dog. But as development 

 advances, all the parts acquire their speciality, till at 

 length you have the embrj'o converted into the form of 

 the parent from which it started. So that you see, 

 this living animal, this horse, begins its existence as 

 a minute particle of nitrogenous matter, which, being 

 supplied with nutriment (derived, as I have shown, 

 from the inorganic world), grows up according 

 to the special type and construction of its parents, 

 works and undergoes a constant waste, and that waste 

 is made good by nutriment derived from the inorganic 

 world ; the waste given off in this way being directly 

 added to the inorganic world. Eventually the animal 

 itself dies, and, by the process of decomposition, its 

 whole body is returned to those conditions of inorganic 

 matter in which its substance originated. 



This, then, is that which is true of every living 

 form, from the lowest plant to the highest animal — to 

 man himself. You might define the life of every one 

 in exactly the same terms as those which I have now 

 used ; the difference between the highest and the 

 lowest being simply in the complexity of the develop- 

 mental changes, the variety of the structural forms, 



b2 



